# Primer bulb goes flat



## Smackdaddy53 (Dec 31, 2012)

The primer bulb or your tank vent probably isn’t working.


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## wrinklestar (May 7, 2015)

Tank not venting, did you try running with the cap loose or off?


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## Backcountry 16 (Mar 15, 2016)

Same gas tank that I used on the Spear without an issue so the tanks out and brand new industrial gas line so I am pretty sure that's out also.


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## Tautog166 (Jul 7, 2018)

Backcountry 16 said:


> Same gas tank that I used on the Spear without an issue so the tanks out and brand new industrial gas line so I am pretty sure that's out also.


Did you try? Wouldn’t rule it out until you did. Then you could be sure.


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## Backcountry 16 (Mar 15, 2016)

It's definitely not the tank as it was used on another boat without a issue and the gas line is brand new 3/8 tubing fresh fittings on tank and motor so I am at a loss as to the issue.


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## Plantation (Nov 24, 2015)

I would try the tank connection as well as what others said with the vent. I know its never failed you before but things do happen. I bought a new fuel connector for my old boat and I found out it wasnt seating properly after a similar issue.


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## Backcountry 16 (Mar 15, 2016)

Plantation said:


> I would try the tank connection as well as what others said with the vent. I know its never failed you before but things do happen. I bought a new fuel connector for my old boat and I found out it wasnt seating properly after a similar issue.


I will check just weird to never have an issue with any other boat I am contemplating my Mercury 25 I know that'll pull the gas back for sure.


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## East Cape (Sep 3, 2015)

Like others have said... its either the tank is not open on the vent, or bad primer bulb or connection of the hose to tank or motor could also fail. It's not the engine based off what I've seen if primer bulb is going flat after a few minutes of running.


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## Backcountry 16 (Mar 15, 2016)

It runs in the yard with no issue ran about 45 minutes the other day as soon as there is a load it acts up head scratcher.That's why I was hoping someone was having the same issue. I will be hanging the 25 on the bacj whenever I get back from our cruise.


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## AZ_squid (Mar 14, 2018)

If the tank is portable and isn't venting it will look sucked in and make a sucking noise as soon as you open it. Had the same issue with my yamaha 20 4 stroke a while back, swapped the tank and the problem stopped.


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## Backwater (Dec 14, 2014)

Backcountry 16 said:


> I picked up a mint condition gladesman last month and have had it out a few times the first time I took it out it ran for about 30 minutes then the primer bulb lost it's prime. I have replaced the tank,bulb,gas line and all fittings still having the same issue. The fuel tank is up front and the run is about 16 feet so my theroy is that the motor is having a hard time pulling the gas that far for reference the motor is a 05 Yami 15 4 stroke. What say you microskiffers?


Tank vent problem. Also, have your fuel pump checked.


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## Guest (Mar 14, 2019)

Ok Jimmy, you answered your own question brother! 3/8” fuel hose and a 16’ run is your problem. The little pump can not pull the weight of the fuel that far! Drop down to a 5/16” fuel hose and your problem will most likely be remedied! You can test the theory by putting the tank in the back with a short hose and run it before replacing all the fuel line, but I am willing to bet a sammich that this is your problem!


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## Capnredfish (Feb 1, 2012)

If the bulb is sucked in after running a load, that’s because you are pulling more gas than air is entering the tank/vent. Basically a vacuum and at some point the fuel pump won’t pull any more. Everything works till it breaks. Don’t rule out tank or vent issue just because it used to work.
However I think Boatbrains knows more about boat motors than me.


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## Backcountry 16 (Mar 15, 2016)

Boatbrains said:


> Ok Jimmy, you answered your own question brother! 3/8” fuel hose and a 16’ run is your problem. The little pump can not pull the weight of the fuel that far! Drop down to a 5/16” fuel hose and your problem will most likely be remedied! You can test the theory by putting the tank in the back with a short hose and run it before replacing all the fuel line, but I am willing to bet a sammich that this is your problem!


Thanks boatbrains I'll try that


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## flyclimber (May 22, 2016)

Maybe that's what I need to try with my HB.... drop to 5/16 on all my hosing.


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## Boneheaded (Oct 4, 2017)

my jonboat has tank up front, with an inline filter, when i get to bout a quarter tank, i start having issues as well. check fuel level.

Also

My hobie skiff did the same thing about 5 miles off ft lauderdale, bumping around made the fuel connector from the tank to fuel line got clogged wit a tiny piece of silicone... something is clogged.

Try running a smaller line too! im running 1/4 or 5/8 in both boats.


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## Finsleft258 (Oct 7, 2018)

Also check to see if you are "making oil" or your oil smells like fuel. I have had two Yamaha 15s of that generation come through with perforated fuel pump membranes. They would run but couldn't pull enough fuel at high throttle.


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## Guest (Mar 14, 2019)

Finsleft258 said:


> Also check to see if you are "making oil" or your oil smells like fuel. I have had two Yamaha 15s of that generation come through with perforated fuel pump membranes. They would run but couldn't pull enough fuel at high throttle.


Yes, this too!


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## Guest (Mar 14, 2019)

Finsleft258 said:


> Also check to see if you are "making oil" or your oil smells like fuel. I have had two Yamaha 15s of that generation come through with perforated fuel pump membranes. They would run but couldn't pull enough fuel at high throttle.


Yes, this too!


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## Backcountry 16 (Mar 15, 2016)

Finsleft258 said:


> Also check to see if you are "making oil" or your oil smells like fuel. I have had two Yamaha 15s of that generation come through with perforated fuel pump membranes. They would run but couldn't pull enough fuel at high throttle.


I will check the oil when I get home today thanks.


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## CPurvis (Apr 6, 2016)

Finsleft258 said:


> Also check to see if you are "making oil" or your oil smells like fuel. I have had two Yamaha 15s of that generation come through with perforated fuel pump membranes. They would run but couldn't pull enough fuel at high throttle.


I had this issue with a 15 hp mercury. Had same symptoms.


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## Smackdaddy53 (Dec 31, 2012)

When under a load the motor is demanding more fuel and the pump is sucking harder. A lot of outboard issues don’t show themselves on the hose or at idle but when you put the hammer down they show themselves. I could see how too small a fuel hose would cause fuel delivery issues on a small outboard and a long tank run but why would the bulb go flat? My fuel hose on the 70 is 5/16” and the run is about 17’ because of high motor mounting.


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## Finsleft258 (Oct 7, 2018)

Smackdaddy53 said:


> When under a load the motor is demanding more fuel and the pump is sucking harder. A lot of outboard issues don’t show themselves on the hose or at idle but when you put the hammer down they show themselves. I could see how too small a fuel hose would cause fuel delivery issues on a small outboard and a long tank run but why would the bulb go flat? My fuel hose on the 70 is 5/16” and the run is about 17’ because of high motor mounting.


I missed that part. I only saw the lost prime. In your case, there is one of the following:

1: collapsed or obstructed fuel line before the primer bulb.
2: faulty valve in the primer bulb. 
3: faulty anti-siphon valve.
4: fouled vent.
5: fouled pick--up in tank.


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## Finsleft258 (Oct 7, 2018)

Post a pic of the fuel line. Something is not jiving.


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## Finsleft258 (Oct 7, 2018)

Also, is this one of the new EPA compliant tanks?


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## Backcountry 16 (Mar 15, 2016)

CPurvis said:


> I had this issue with a 15 hp mercury. Had same symptoms.





Finsleft258 said:


> Also, is this one of the new EPA compliant tanks?


Yes I have tried a new tank and an old tank but the new tank was used on another boat without an issue.


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## Backcountry 16 (Mar 15, 2016)

Here you go


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## Myakka Red (Jan 4, 2017)

Another possible reason...the light grey fuel line you show may have a thin clear plastic liner inside. This over time collapses and turns to sh**. Been there.


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## Guest (Mar 15, 2019)

So to be clear, is the bulb sucking flat or just losing prime?


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## Backcountry 16 (Mar 15, 2016)

Myakka Red said:


> Another possible reason...the light grey fuel line you show may have a thin clear plastic liner inside. This over time collapses and turns to sh**. Been there.


Brand new fuel line no inner tube had that issue also before. It did the same thing with the old fuel line also I believe it is in the motor as suggested by someone else. I have decided to put the 25 on it and pull off the 15 that will definitely fix the problem as I know the 25 will pull the gas that far. Now I just need to see if a 9 gallon tank will fit under the front deck.


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## Backcountry 16 (Mar 15, 2016)

Boatbrains said:


> So to be clear, is the bulb sucking flat or just losing prime?


Collapses but not all the way flat.


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## Marsh Pirate (Sep 15, 2016)

If the bulb is collapsing, I'm having a hard time seeing this as a motor issue.


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## Guest (Mar 15, 2019)

Jimmy, if the bulb is collapsing/sucking flat then your problem is most definitely a restriction before the bulb. I can say this without a doubt brother! I misread your posts and thought it was losing prime.


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## flyclimber (May 22, 2016)

Backcountry 16 said:


> Brand new fuel line no inner tube had that issue also before. It did the same thing with the old fuel line also I believe it is in the motor as suggested by someone else. I have decided to put the 25 on it and pull off the 15 that will definitely fix the problem as I know the 25 will pull the gas that far. Now I just need to see if a 9 gallon tank will fit under the front deck.


That gladesman is gonna skip along with the 25! You might need to wet sand a pad to keep some traction


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## Marsh Pirate (Sep 15, 2016)

Boatbrains said:


> Jimmy, if the bulb is collapsing/sucking flat then your problem is most definitely a restriction before the bulb. I can say this without a doubt brother! I misread your posts and thought it was losing prime.


I agree 100%!


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## Finsleft258 (Oct 7, 2018)

That full line you posted most certainly does have a liner, every B1-15 line has it with the exception of Sierra Silverado 4000 and a certain Gates love. Also, B1-15 is soft in general. Go to an A1-15. If your running long runs, you need LARGER hose. It has nothing to do with the weight of the fuel, but the pressure loss caused be fluid friction within the hose. I don't see the diameter as the issue however.


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## Finsleft258 (Oct 7, 2018)

It could be the disconnect on the tank.


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## Backcountry 16 (Mar 15, 2016)

I would agree if it hadn't happened with 2 different tanks 2 different gas lines 2 different primer bulbs and 2 different set of fittings that's the only reason I posted it I am halfway smart and I use that term losely the only constant is the motor.


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## Finsleft258 (Oct 7, 2018)

Ok. Photos are helping. I have also experienced problems with the Sierra bulbs and also Moeller bulbs (those more so) in a few application where they were sucking flat and no other issues were found. The compliant bulbs tend to be more pliable than some of the older ones. The best two bulbs I've found are the Yamaha (by far) and the Mercury. They are ungodly expensive by comparison unfortunately. It might be that simple.


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## Guest (Mar 15, 2019)

I’m a fan of the Merc bulbs and the brp bulbs myself.


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## Boneheaded (Oct 4, 2017)

Maybe part of problem but the diameter in fuel line is too big, the Diaphram on youre fuel pump is probably little bigger than a silver dollar, sucking fuel 15 feet is like throwing a hotdog down a hall way.


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## SomaliPirate (Feb 5, 2016)

I'm an idiot so take this for what it's worth, but mine kept losing prime and collapsing a little a couple of years ago. I replaced the Walmart special bulb with a Yamaha bulb and was good to go. I replace bulbs as part of annual maintenance now.


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## Finsleft258 (Oct 7, 2018)

Boatbrains said:


> Ok Jimmy, you answered your own question brother! 3/8” fuel hose and a 16’ run is your problem. The little pump can not pull the weight of the fuel that far! Drop down to a 5/16” fuel hose and your problem will most likely be remedied! You can test the theory by putting the tank in the back with a short hose and run it before replacing all the fuel line, but I am willing to bet a sammich that this is your problem!





Boneheaded said:


> Maybe part of problem but the diameter in fuel line is too big, the Diaphram on youre fuel pump is probably little bigger than a silver dollar, sucking fuel 15 feet is like throwing a hotdog down a hall way.


OK. Gonna try and hit this misconception. Let me know if you have more questions.

With fluids, pressure is dependent upon the head (vertical rise) only. The weight of the fluid due to the diameter of the line has no bearing. A pump that is capable of pushing 115 feet of head will do so through any diameter of hose, pipe, line. 

The other items that dictate pump efficiency are velocity (high flow velocity is different from flow rate), drag within the system (usually from material limitations--in this case hose), radius changes (tight 90 degree turns can cause up to 50% in pressure drop). These items remain true on pressure and suction systems. 

For an outboard fuel pump, regardless of the size of the fuel pump inlet, the resistance within the system will ALWAYS be less with a larger diameter fuel line running from the tank to as far along the system as possible.


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## Boneheaded (Oct 4, 2017)

According to a textbook maybe a misconception, but in real world application downsizing fuel line solved my fuel delivery issues, much more pressure coming through my lines. Try blowing a mouth full water through a piece of 1/2" pvc then plow it through a straw...Remember our fuel tanks are generally below the motor so its sucking up hill too


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## Marsh Pirate (Sep 15, 2016)

I was a industrial firefighter for over 25 years. We had pumps(4) that could pump 6000 gallons a minute. We often pumped water over a 1/2 mile. The argument here about reducing the line size to improve pump capacity is totally wrong. Bigger is always better.


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## Finsleft258 (Oct 7, 2018)

Boneheaded said:


> According to a textbook maybe a misconception, but in real world application downsizing fuel line solved my fuel delivery issues, much more pressure coming through my lines. Try blowing a mouth full water through a piece of 1/2" pvc then plow it through a straw...Remember our fuel tanks are generally below the motor so its sucking up hill too


You're proving my point. You see an increase of water velocity, not pressure, by blowing through the straw. Downsizing your fuel lines likely allowed you to have better radii and also prime more easily since the fuel is less compressible than air in the lines.


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## Finsleft258 (Oct 7, 2018)

Marsh Pirate said:


> I was a industrial firefighter for over 25 years. We had pumps(4) that could pump 6000 gallons a minute. We often pumped water over a 1/2 mile. The argument here about reducing the line size to improve pump capacity is totally wrong. Bigger is always better.


I specified big ass sea strainers for commercial vessels. Flow is poorly understood.


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## Guest (Mar 15, 2019)

Finsleft258 said:


> OK. Gonna try and hit this misconception. Let me know if you have more questions.
> 
> With fluids, pressure is dependent upon the head (vertical rise) only. The weight of the fluid due to the diameter of the line has no bearing. A pump that is capable of pushing 115 feet of head will do so through any diameter of hose, pipe, line.
> 
> ...


I understand what your sayin, I just know that these diaphram pumps will not “in most cases” pull fuel this distance through a large diameter line, they will however pull it through a smaller line which is why I said try a smaller line. I will note, that if the pump is pulling the ball down that fuel line diameter is not the problem.


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## Finsleft258 (Oct 7, 2018)

Boatbrains said:


> I understand what your sayin, I just know that these diaphram pumps will not “in most cases” pull fuel this distance through a large diameter line, they will however pull it through a smaller line which is why I said try a smaller line. I will note, that if the pump is pulling the ball down that fuel line diameter is not the problem.


I agree, but it's not for the pressure reasons. It's because of the flex in the lines (i.e. the line not remaining rigid through its cross-section) and the air in the system. I've had much better luck with A1-15 lines because they are more stable dimensionally, thus eliminating one of these problems. If it was hard plumbed (which we obviously can't do) and bled of all air the fuel pumps could pull through any size pipe.


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## Guest (Mar 15, 2019)

Guys, we are pulling fuel on this side of the pump. These are diaphram pumps that will just float/seize if lift head is too high. There is a very good reason that engine manufactures state a specific distance and also spec fuel hose if you read their rigging guides. I am no fluid dynamics specialist nor a plumber, i do know what the engine manufacturer says in most cases though. If “bigger” was always better they would put a 3/8” line on a 2hp engine and a 5/8 or bigger on a v6. I only know what I have experienced, what the factories have taught me, and what I’ve read in rigging guides. These little diaphram pumps simply do not have the umph to pull fuel these distances. The way this problem is overcome is in fact by reduction of fuel line diameter. Bandaid? Maybe, but it usually works.


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## Smackdaddy53 (Dec 31, 2012)

Finsleft258 said:


> I missed that part. I only saw the lost prime. In your case, there is one of the following:
> 
> 1: collapsed or obstructed fuel line before the primer bulb.
> 2: faulty valve in the primer bulb.
> ...


I wasn’t referring to my setup having primer bulb issues, I was posting what I have and it works flawlessly.


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## Finsleft258 (Oct 7, 2018)

Boatbrains said:


> Guys, we are pulling fuel on this side of the pump. These are diaphram pumps that will just float/seize if lift head is too high. There is a very good reason that engine manufactures state a specific distance and also spec fuel hose if you read their rigging guides. I am no fluid dynamics specialist nor a plumber, i do know what the engine manufacturer says in most cases though. If “bigger” was always better they would put a 3/8” line on a 2hp engine and a 5/8 or bigger on a v6. I only know what I have experienced, what the factories have taught me, and what I’ve read in rigging guides. These little diaphram pumps simply do not have the umph to pull fuel these distances. The way this problem is overcome is in fact by reduction of fuel line diameter. Bandaid? Maybe, but it usually works.


Head does not change with line diameter. Example, 33 feet of water is the same pressure whether it is a 2" pipe or 33 feet of ocean depth (provided it is the same water, i.e. salt vs. fresh). 

I fully agree that a smaller line can provide a solution--it's for the reasons I previously stated (better radius in some installations, less pumping loss due to hose deformation, less air in the system). 

As for the fuel pumps, some of these small outboards have nearly identical pumps to their larger brethren, albeit smaller fuel inlet/outlet nipples. My assumption is they are not specifying larger lines due to space issues and overall costs. There have been outboards that have needed larger lines or lift pumps in the past as well. J/E looper V6 in certain installations and the V8 as well have needed additional pump capacity. 

I'm guessing the culprit here is the primer bulb. The new ones blow a hard one. If it's not that, then the distance is just too long for that pump...or the pump could be failing. In any case, the fuel pump on the 25 is grossly undersized as it shares a similar design to the one used on 4/5 hp Merc/Yam/Tohasu engines.


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## Finsleft258 (Oct 7, 2018)

Smackdaddy53 said:


> I wasn’t referring to my setup having primer bulb issues, I was posting what I have and it works flawlessly.


Got ya.


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## Mike C (Feb 27, 2017)

Boatbrains said:


> Guys, we are pulling fuel on this side of the pump. These are diaphram pumps that will just float/seize if lift head is too high. There is a very good reason that engine manufactures state a specific distance and also spec fuel hose if you read their rigging guides. I am no fluid dynamics specialist nor a plumber, i do know what the engine manufacturer says in most cases though. If “bigger” was always better they would put a 3/8” line on a 2hp engine and a 5/8 or bigger on a v6. I only know what I have experienced, what the factories have taught me, and what I’ve read in rigging guides. These little diaphram pumps simply do not have the umph to pull fuel these distances. The way this problem is overcome is in fact by reduction of fuel line diameter. Bandaid? Maybe, but it usually works.


If you don't believe what he's saying about fluid suction from a pump, try this:
Get a full glass of water, a 4" section of 1" PVC pipe and a straw. In fact, get two straws. One skinny one from the grocery store and one from McDonald's. 
Place the skinny straw in the glass and have a sip.
Easy enough, right? 
Take the McDonald's straw and do the same. Easy enough, but the skinny straw was easier. 
Top off the glass of water and put that short section of PVC and have a sip. 
It ain't so easy to move 4oz of water, is it? 
Liquid movement works on pressure, volume and weight.
Weight of the fuel from above can create head (or positive) pressure. 
Weight from below requires extra suction pressure to overcome it. 
Think of it this way, you don't siphon fuel to a container above the supply tank. You always set the receiver tank below so the head pressure keeps the flow going. 

Can I make it any clearer than that?


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## Finsleft258 (Oct 7, 2018)

Mike C said:


> If you don't believe what he's saying about fluid suction from a pump, try this:
> Get a full glass of water, a 4" section of 1" PVC pipe and a straw. In fact, get two straws. One skinny one from the grocery store and one from McDonald's.
> Place the skinny straw in the glass and have a sip.
> Easy enough, right?
> ...


Mike, please take a look at the pressure drop numbers located here: https://www.michigan.gov/documents/138-139_Vacuum_Drop_13205_7.pdf

This is for vacuum drop as you have pointed out requires additional energy. True. Please note that the vacuum drop DECREASES as pipe size at a given flow rate (not velocity) INCREASES. 

Your example above is not a measure of pressure.


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## Backcountry 16 (Mar 15, 2016)

Sorry guys for gas talk 101. I think I will try another primer bulb as that bulb really never gets hard all the way so it very well could be the bulb even though I have tried 2.


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## makin moves (Mar 20, 2010)

Backcountry 16 said:


> Sorry guys for gas talk 101. I think I will try another primer bulb as that bulb really never gets hard all the way so it very well could be the bulb even though I have tried 2.


Got more than you bargain for.


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## Backcountry 16 (Mar 15, 2016)

makin moves said:


> Got more than you bargain for.


Amen


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## Guest (Mar 15, 2019)

makin moves said:


> Got more than you bargain for.


Microskiff never disappoints!


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## Backcountry 16 (Mar 15, 2016)

Boatbrains said:


> Microskiff never disappoints!


 Hasn't yet


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## Mike C (Feb 27, 2017)

Mike C said:


> If you don't believe what he's saying about fluid suction from a pump, try this:
> Get a full glass of water, a 4" section of 1" PVC pipe and a straw. In fact, get two straws. One skinny one from the grocery store and one from McDonald's.
> Place the skinny straw in the glass and have a sip.
> Easy enough, right?
> ...


Weight from below requires extra suction VOLUME to overcome it.

Sorry fellas. I misspoke what I wrote above, it's been a while since I had to figure this stuff out. 
Vacuum pressure was incorrect, it's actually volume that gets fluid moving through a larger pipe/tube.
Once it's moving it's pretty easy to keep it going as long as the pump works correctly. 

The boat in question has a working pump and most likely the primer bulb is suitable too. 
If the bulb is going flat, then the tank is not venting properly or the line internal diameter is compromised in some way. Pinch, lining or any number of things.


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## Finsleft258 (Oct 7, 2018)

Backcountry 16 said:


> Sorry guys for gas talk 101. I think I will try another primer bulb as that bulb really never gets hard all the way so it very well could be the bulb even though I have tried 2.


Likewise. Didn't mean to derail the thread. My apologies everyone.


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## Finsleft258 (Oct 7, 2018)

Mike C said:


> Weight from below requires extra suction VOLUME to overcome it.
> 
> Sorry fellas. I misspoke what I wrote above, it's been a while since I had to figure this stuff out.
> Vacuum pressure was incorrect, it's actually volume that gets fluid moving through a larger pipe/tube.
> ...


You got it! I'm thinking primer, restriction, or the tank disconnect (air leak).


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## Backcountry 16 (Mar 15, 2016)

Finsleft258 said:


> Likewise. Didn't mean to derail the thread. My apologies everyone.


No worries that's why I posted it no apologies needed. This was my last resort as I have ran out of ideas.


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## Finsleft258 (Oct 7, 2018)

Backcountry 16 said:


> No worries that's why I posted it no apologies needed. This was my last resort as I have ran out of ideas.


If the primer doesn't solve it, I would seriously consider doing a barb at the tank rather than the disconnect. I know it makes refueling a bitch, but those brass ones leak air like crazy if the O-Ring on the female side even thinks about being damaged. The plastic Attwood one isn't too terrible if you absolutely need a disconnect.

I doubt it's that though since the primer is sucking flat...


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## State fish rob (Jan 25, 2017)

I got a brother n law that doesn’t know the difference between a tank disconnect vs barb . Most expensive 6 gal I never bought.


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## 17376 (May 5, 2017)

Borrow a portable tank from a friend. See if it runs on a portable tank directly to the engine. If it does then it is somewhere between the fuel line connection at the engine and a tank. If it does not run it’s most likely fuel pump related


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## LowHydrogen (Dec 31, 2015)

I won't jump into the hydrodynamics conversation. I will say I've had a boat do this before and it was a stray blob of silicone in the tank. Boat would run awesome at low RPM, as soon as load increased it would get sucked over the pickup, bulb would collapse, and motor would stall. 

I've now got a little 9.9 Merc that is doing the same thing, brand new tank, line etc. 

Try this. Take the fitting off the line at the tank, and stick just the hose down in the tank. It worked on my 9.9 and it ran fine. I still haven't figured out what the deal with the tank fitting or pickup is, but I know it's jacked up somewhere right there.

Let us know what you figure out.


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## CPurvis (Apr 6, 2016)

Marsh Pirate said:


> I was a industrial firefighter for over 25 years. We had pumps(4) that could pump 6000 gallons a minute. We often pumped water over a 1/2 mile. The argument here about reducing the line size to improve pump capacity is totally wrong. Bigger is always better.


That depend on if you are looking for pressure or volume. If you are looking for volume than yes bigger is better. If you are looking for pressure than you will need to reduce the size of the orifice. And in the case of a fuel line nothing is being pushed or pulled you are priming by removing air and atmospheric pressure is brings the fuel to the fuel pump which pumps the fuel where it needs to go. Any introduction of air will cause a loss of prime.


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## CPurvis (Apr 6, 2016)

CPurvis said:


> That depend on if you are looking for pressure or volume. If you are looking for volume than yes bigger is better. If you are looking for pressure than you will need to reduce the size of the orifice. And in the case of a fuel line nothing is being pushed or pulled you are priming by removing air and atmospheric pressure is brings the fuel to the fuel pump which pumps the fuel where it needs to go. Any introduction of air will cause a loss of prime.





CPurvis said:


> That depend on if you are looking for pressure or volume. If you are looking for volume than yes bigger is better. If you are looking for pressure than you will need to reduce the size of the orifice. And in the case of a fuel line nothing is being pushed or pulled you are priming by removing air and atmospheric pressure is brings the fuel to the fuel pump which pumps the fuel where it needs to go. Any introduction of air will cause a loss of prime.


Damn it i knew i should never post a comment before reading entire thread. Disregard. Carry on! Buy the bulb. Hope everythimg works out.


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## Backwater (Dec 14, 2014)

Ok boys, this is going to seem like a dumb question. Jimmy, did you check the flow direction arrow on the bulb to make sure it points towards the direction of the motor? 

i.e. - Tank------bulb-->--------Motor



I like the idea of changing the bulb to a Yamaha bulb. In my experience with yami's, the fuel pumps can be down right picky. If the old tank works just fine at the same distance to the motor with the same setup, vs, the new tank, well, there you have it and just change out the tank. But if things are the same, have an OB mechanic (or yourself) take apart the fuel pump to see if there is any issues there in the pump (or just swap it all together. Otherwise, I'd take it over to the boys at *Fowler Marine* instead of scratching a hole in your head.


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## Backcountry 16 (Mar 15, 2016)

Backwater said:


> Ok boys, this is going to seem like a dumb question. Jimmy, did you check the flow direction arrow on the bulb to make sure it points towards the direction of the motor?
> 
> i.e. - Tank------bulb-->--------Motor
> 
> ...


10 4 flow is correct and neither of the tanks are working properly.


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## Backwater (Dec 14, 2014)

Backcountry 16 said:


> 10 4 flow is correct and neither of the tanks are working properly.


Yamaha bulb! Also install a new "Yamaha" (from Yamaha) fuel line connector at the OB on your fuel line. Check to see if that worked. Are you using the same fuel line on both tanks? If yes, then that is your common denominator. If not, then replace your in-line fuel filter INSIDE the cowling near the fuel pump (small and PITA to remove). If that solves your problem, then your good. If not, it's probably your fuel pump, like I mentioned on my 1st reply.

F-O-W-L-E-R---M-A-R-I-N-E......... These guys know what they are doing, honest and reasonable. Just sayin.... 

For Yamaha Parts shipped to you for less... Pro Marine. These guys are close to me (I can ride a bike to them) and are cheaper than most on-line Yamaha parts suppliers.
http://parts.promarineusa.com/CGI-BIN/LANSAWEB?PROCFUN+WORDPR01+WEBFUNC+M50


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## dafjib (Mar 7, 2019)

If all else fails ,get a inline pump ,it helped me out a lot ,and they dont cost much .


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## 17376 (May 5, 2017)

Whatever you do don’t get an in-line pump.. the pump should be able to pull it. Pump the bulb up. Once it is pumped up and full of gas in the line take the bulb off stick the hose directly in a gas can and run it and the pump will do all the work you do not need a bulb to test. That will eliminate whether it is the long pull, bulb or if the pump is bad or going bad.


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## Mckee (Jan 10, 2019)

After all the science will we ever hear what the problem was?


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## Backcountry 16 (Mar 15, 2016)

Mckee said:


> After all the science will we ever hear what the problem was?


My schedule hasn't allowed me to investigate any further maybe this weekend I will look at it closer.


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## Jim Lenfest (Jul 20, 2016)

I have read 2 pages of this thread, but not completed it. Apologies if this has already been mentioned. First, if the bulb is getting sucked flat, the fuel pump is fine. If the tank is venting properly, then check the fittings/hose connections. Some of the fuel line is two part. A plastic inner hose and then a more rubbery outer hose. Oftentimes the 2 become de-laminated, especially at the ends where connections are. Everything works fine, until a little extra suctions sucks the inner plastic hose flat and fuel can no longer travel through the hose. From the outside, you see nothing, because the outer rubber hose, remains in it normal shape. Also, sometimes you slide the hose on the barb, and the inner plastic hose slides inward, never getting on the barb. The clamp is placed of the outer hose only. Then the inner hose opens and closes like a check valve in your heart. That is what happened to me. My dealer blames the de-lamination on the alcohol in the fuel these days. Also here in Maine, we use our boats year round with the temperatures being 20 below one day and 50 above the next. Just havoc on plastic and rubber parts.


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## Backcountry 16 (Mar 15, 2016)

Jim Lenfest said:


> I have read 2 pages of this thread, but not completed it. Apologies if this has already been mentioned. First, if the bulb is getting sucked flat, the fuel pump is fine. If the tank is venting properly, then check the fittings/hose connections. Some of the fuel line is two part. A plastic inner hose and then a more rubbery outer hose. Oftentimes the 2 become de-laminated, especially at the ends where connections are. Everything works fine, until a little extra suctions sucks the inner plastic hose flat and fuel can no longer travel through the hose. From the outside, you see nothing, because the outer rubber hose, remains in it normal shape. Also, sometimes you slide the hose on the barb, and the inner plastic hose slides inward, never getting on the barb. The clamp is placed of the outer hose only. Then the inner hose opens and closes like a check valve in your heart. That is what happened to me. My dealer blames the de-lamination on the alcohol in the fuel these days. Also here in Maine, we use our boats year round with the temperatures being 20 below one day and 50 above the next. Just havoc on plastic and rubber parts.


Unlikely as it has happened with 2 different gas lines,tanks, fittings and bulb.


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## Smackdaddy53 (Dec 31, 2012)

What’s the constant then? If you have changed all that twice and it persists you have an issue further up stream or the size of fuel line is wrong.


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## Marsh Pirate (Sep 15, 2016)

I sure hope Backcountry definitively finds the problem and documents it here. I'm extremely curious to learn what he finds the problem to be.


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## Backcountry 16 (Mar 15, 2016)

Smackdaddy53 said:


> What’s the constant then? If you have changed all that twice and it persists you have an issue further up stream or the size of fuel line is wrong.


 The only thing I can think of is my original suspicion is the motor I am hoping to look at it this weekend.


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## Smackdaddy53 (Dec 31, 2012)

Backcountry 16 said:


> The only thing I can think of is my original suspicion is the motor I am hoping to look at it this weekend.


How could it be the motor? The fuel pump is pulling fine if it’s flattening the bulb. I’d look at the hose size from the bulb to the tank.


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## Backcountry 16 (Mar 15, 2016)

Marsh Pirate said:


> I sure hope Backcountry definitively finds the problem and documents it here. I'm extremely curious to learn what he finds the problem to be.


Will definitely do that


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## Backcountry 16 (Mar 15, 2016)

Smackdaddy53 said:


> How could it be the motor? The fuel pump is pulling fine if it’s flattening the bulb. I’d look at the hose size from the bulb to the tank.


3/8 hose. I am taking off the Yami anyways too slow so if I put on the 25 and it works then it's solved if not back to the drawing board.


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## Backcountry 16 (Mar 15, 2016)

I am going to get a better primer bulb even though that one is new looking into a Mercury and Yamaha.


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## Backwater (Dec 14, 2014)

Jim Lenfest said:


> I have read 2 pages of this thread, but not completed it. Apologies if this has already been mentioned. First, if the bulb is getting sucked flat, the fuel pump is fine. If the tank is venting properly, then check the fittings/hose connections. Some of the fuel line is two part. A plastic inner hose and then a more rubbery outer hose. Oftentimes the 2 become de-laminated, especially at the ends where connections are. Everything works fine, until a little extra suctions sucks the inner plastic hose flat and fuel can no longer travel through the hose. From the outside, you see nothing, because the outer rubber hose, remains in it normal shape. Also, sometimes you slide the hose on the barb, and the inner plastic hose slides inward, never getting on the barb. The clamp is placed of the outer hose only. Then the inner hose opens and closes like a check valve in your heart. That is what happened to me. My dealer blames the de-lamination on the alcohol in the fuel these days. Also here in Maine, we use our boats year round with the temperatures being 20 below one day and 50 above the next. Just havoc on plastic and rubber parts.


Backcountry, I think this can be a strong possibility, especially when you said he tried 2 different tanks and are getting the same results. But remember, you were using the same fuel line.

Someone here mentioned borrowing someones fuel tank to try that one out as well. But if you do that, also try a different line. You never know what kind of fuel was run in that tank by the previous owner and back in the 90's and early 2000's, some lines still had problems with alcohol.

If you are changing out the bulb, ya might as well change out the line and put the whole problem possibility to rest. Lines are cheap, especially when you are miles deep in the Glades when nobody is around to drag yer ass back to the ramp! 

I think we will all donate to your fuel line fund to put this thread out of it's misery and get you done, fixed and happy! I got $5 I'll contribute to either the hose or the beer!


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## Tautog166 (Jul 7, 2018)

Backcountry 16 said:


> The only thing I can think of is my original suspicion is the motor I am hoping to look at it this weekend.


You’ve had it in for this motor from the get go. May as well put your Mercury that you have and see how that works for you.


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## SomaliPirate (Feb 5, 2016)

Walter Lee said:


> You’ve had it in for this motor from the get go. May as well put your Mercury that you have and see how that works for you.


This thread is full of anti-Yamaha microaggressions.


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## Smackdaddy53 (Dec 31, 2012)

SomaliPirate said:


> This thread is full of anti-Yamaha microaggressions.


This aggression will not stand!


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## Jim Lenfest (Jul 20, 2016)

Backcountry 16 said:


> Unlikely as it has happened with 2 different gas lines,tanks, fittings and bulb.


My thought exactly, however, I am not convinced that he has changed all of the hose. What I described actually happened to me, and according to my dealer, it has happened many times in our area. Hose de-lamination was a common problem shortly after alcohol was introduced to the fuel. You also have the pick up tube in the tank to consider as well.


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## Backcountry 16 (Mar 15, 2016)

I replaced the fitting on the tank to a barbed one with a hose clamp( no quick connect now) ran much better but still lost some of its prime later in the day. I am swapping the battery mount and tank in front and that will shorten the hose up and I am hoping that will solve the issue. I did learn two lessons yesterday a gladesman is super light big snook are strong and mirrodines lures have shitty hooks


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## SomaliPirate (Feb 5, 2016)

Backcountry 16 said:


> I replaced the fitting on the tank to a barbed one with a hose clamp( no quick connect now) ran much better but still lost some of its prime later in the day. I am swapping the battery mount and tank in front and that will shorten the hose up and I am hoping that will solve the issue. I did learn two lessons yesterday a gladesman is super light big snook are strong and mirrodines lures have shitty hooks
> View attachment 67020
> View attachment 67022


Whenever I have a mirrolure with those black hooks, the first thing I do is change them out to the old original style. The black ones are sharp, but they'll rust out in ten minutes.


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## Backcountry 16 (Mar 15, 2016)

SomaliPirate said:


> Whenever I have a mirrolure with those black hooks, the first thing I do is change them out to the old original style. The black ones are sharp, but they'll rust out in ten minutes.


10 4 already bought replacements that won't happen again.


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## Backcountry 16 (Mar 15, 2016)

Okay so it's update time I replaced the bulb with a Mercury Quicksilver bulb and it ran much better but eventually would pull the bulb flat later in the day. I replaced the motor with the 25 and have has it out twice and haven't had an issue yet bulb stays primed all day. And on a side note I gained about 15 mph hit 31 on the gps.


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## makin moves (Mar 20, 2010)

That's the motor you wanted on it the whole time and you can depend on. Win win! I bet thats a fun ride clipping along at 31 mph in that.


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## Backcountry 16 (Mar 15, 2016)

makin moves said:


> That's the motor you wanted on it the whole time and you can depend on. Win win! I bet thats a fun ride clipping along at 31 mph in that.


Yes it was pretty crazy I mainly ran half throttle most of the day and was criuising around 25.


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## Tigweld (Oct 26, 2017)

Boat only ran 16 mph with the Yamaha??


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## Backcountry 16 (Mar 15, 2016)

Tigweld said:


> Boat only ran 16 mph with the Yamaha??


I saw 18 one time with the 15 lightly loaded.


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## Tigweld (Oct 26, 2017)

Slow


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## Backcountry 16 (Mar 15, 2016)

Tigweld said:


> Slow


Not anymore


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## Backcountry 16 (Mar 15, 2016)

Tigweld said:


> Slow


Not anymore


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