# Engine Sputtering...still



## BrownDog (Jun 22, 2019)

Optimax may be over my head as I typically work on carbed engines.

Some easy things to try:
Find a dark area or night and run it, look for any electrical arcing.
Make sure all your fuel lines, filters, plugs are tightly fitted as it could be an air leak, can shoot carb cleaner around any gaskets as well to see if the sputter goes away too.


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## Smackdaddy53 (Dec 31, 2012)

Yamaha


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## Chad Cohn (Mar 8, 2018)

Smackdaddy53 said:


> Yamaha


Still paying for this one or else I'd have already swapped. Bad thing is there is only one "certified" Yamaha shop in the Austin area and there is no way in HELL I'll buy from them...again. I'm not sure they truly performed all of the "checks" they say they do on this boat as that is where I purchased it. Oh, and the "warranty" I purchased through them was a waste of money too, every time I took it over there for what should've been a warranty issue I was told it wasn't.


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## slewis (Sep 8, 2015)

If you have a battery switch check the connections there.


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## Chad Cohn (Mar 8, 2018)

slewis said:


> If you have a battery switch check the connections there.


Question on that, if that was an issue would my electronics have issues as well?


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## Finsleft258 (Oct 7, 2018)

Chad Cohn said:


> Question on that, if that was an issue would my electronics have issues as well?


No. Those engines need a battery with 1000 MCA capacity. Once it starts to drop too low, the engine will begin to exhibit issues, though usually a voltage alarm will sound. Battery cables are an extremely common culprit. 

Did you ever hook this up to an external tank and see if the problem replicates? The check valve on the tank could be an issue. Also, has the mechanical fuel pump been replaced?


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## Chad Cohn (Mar 8, 2018)

The tank has been ruled out as the culprit as the issue remained on the portable tank. They have not been replaced since I have owned the boat but again my mechanic check everything fuel delivery and we're good on that end. He mentioned he spoke to another fellow mechanic and they have seen similar issues and they've all been electrical. The finding where is the problem we're now facing.


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## lemaymiami (Feb 9, 2007)

The only way you can be certain your existing tank isn’t still a problem is to hook up a known good tank with good fuel line and fuel and run it.. If your trouble is still fuel that second tank will be a sudden magic cure. If the problems still occur then you can at least be sure it’s not fuel related. 

At that point you really need a master tech since there’s quite things that might be causing electrical trouble - from your wiring harness all the way to your battery...


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## Chad Cohn (Mar 8, 2018)

lemaymiami said:


> The only way you can be certain your existing tank isn’t still a problem is to hook up a known good tank with good fuel line and fuel and run it.. If your trouble is still fuel that second tank will be a sudden magic cure. If the problems still occur then you can at least be sure it’s not fuel related.


Issue still existed with portable tank and E free fuel.



lemaymiami said:


> At that point you really need a master tech since there’s quite things that might be causing electrical trouble - from your wiring harness all the way to your battery...


The tech that I had it at last is a master tech with over 30 yrs experience. He did tell me that to diagnose the electrical it would take time. He is still researching on his end and that is where we are.


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## Finsleft258 (Oct 7, 2018)

Once the problem rears its ugly head, does it stay, or does it stop after you back off the throttle?


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## Chad Cohn (Mar 8, 2018)

If I back off it runs fine. It seems that once I go over 3000 rpm it starts.


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## Darkstar (Feb 2, 2017)

Definitely check the battery switch and cables. I had a similar problem on my offshore boat and it ended up being the battery switch. There were no visible signs of damage to the switch but once I replaced it, never had the problem again. Even if that’s not the problem it’s a cheap and easy part to swap out yourself.


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## Smackdaddy53 (Dec 31, 2012)

Check the battery switch, battery terminals, fuse block, every fuse and battery voltage and alternator cables and connections.


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## Chad Cohn (Mar 8, 2018)

So the switch appears to be good, alternator connections are good but I cleaned them anyways. Battery terminals are clean. I looked at every fuse block I could find (on the motor) and no fuses are blown. I'm still working through the connections in the console. FTR, Mako wiring is the absolute shittiest I have seen. I think rats would run from the nest that it is, so I'm trying to clean it up while I'm at it. I'm going to replace the filler hose and vent hoses tomorrow assuming I don't run out of daylight again. So far all connections I have looked at appear to be in working order and dry. Going to look at the sending unit as well and ensure everything is tight and clean. Batteries are out and I'm going to charge them individually and check the voltage on them too. I'm considering replacing the battery switch but haven't decided yet because I don't necessarily want to swap out good parts...yet. I plan on completely dismantling the boat in late Jan or Feb because there are some other issues I want to address as well so if I can get it working for the time being I'll be happy.


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## Finsleft258 (Oct 7, 2018)

Going back through your post history, your troubles seem to have started when you changed the separator. What material is the separator housing? Is it black painted aluminum? Is the coating flaking off? If it is, I can almost guarantee that you are sucking air at the housing/filter interface. Opti electrical issues will rear their head over a wide range of operating conditions and will usually give a voltage alarm. Since you stated the problem only occurs over 3000 rpm, I'm still thinking this is fuel related. Also, you mentioned the VST pumps fine. Does it keep pressure at speed? That's a dynamic test that must be performed with the engine running UNDER LOAD, not just at 3000 rpm. A slight drop (and even a fluctuation) will indicate the need for high pressure pump replacement.

In any case, pictures please. Lots of them. Electrical, fuel system, everything.


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## Chad Cohn (Mar 8, 2018)

The mechanic ran it on the dyno and had gauges on the fuel & air, which were good. Within 10 psi of each other which is what Mercury states it needs to be (90 fuel, 80 air) He was able to replicate the issue but again no drop in psi. Thus his thinking of an electrical issue. Filter housing is not painted where the filter is and I use a dab of 2 stroke oil on the gasket when putting the filter on. I have actually ran with a filter bypass and still received the same result. I'm still working through all of the electrical and hope I can find it's something simple or just a ground that is loose. One time at BPS they did something with the sender (can't remember exactly) and my hope is that maybe they didn't tighten something all the way but again that is just a hope.


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## Finsleft258 (Oct 7, 2018)

Chad Cohn said:


> The mechanic ran it on the dyno and had gauges on the fuel & air, which were good. Within 10 psi of each other which is what Mercury states it needs to be (90 fuel, 80 air) He was able to replicate the issue but again no drop in psi. Thus his thinking of an electrical issue. Filter housing is not painted where the filter is and I use a dab of 2 stroke oil on the gasket when putting the filter on. I have actually ran with a filter bypass and still received the same result. I'm still working through all of the electrical and hope I can find it's something simple or just a ground that is loose. One time at BPS they did something with the sender (can't remember exactly) and my hope is that maybe they didn't tighten something all the way but again that is just a hope.



Fuel sender or fuel pickup? Did you add the water separator or change it? Which came first the problem or the filter change?


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## Finsleft258 (Oct 7, 2018)

Does this dude you're taking it to have the software?


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## Zika (Aug 6, 2015)

A quality Blue Seas battery switch is only $32. Fairly easy to install and you can eliminate that possibility.


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## Finsleft258 (Oct 7, 2018)

The more I look at this, it is definitely a fuel problem. Guardian kicks in at 3000 rpm but will trigger an alarm. Under or over-voltage issues will also trigger an alarm in Mercs. 

There are 3 fuel pumps on this animal. One mechanical lift pump, and two in the VST: a boost pump and a high pressure pump. You're either sucking air somewhere, or the lift or boost pump is on its way out. Do you have a primer bulb on this thing? If so, it shouldn't.


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## Chad Cohn (Mar 8, 2018)

Mech does have the software (O/B mech for 30+ years). It appears to have showed up when I added the water separator.


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## Chad Cohn (Mar 8, 2018)

Finsleft258 said:


> The more I look at this, it is definitely a fuel problem. Guardian kicks in at 3000 rpm but will trigger an alarm. Under or over-voltage issues will also trigger an alarm in Mercs.


No alarms going off at all, which also puzzled the mech.



Finsleft258 said:


> There are 3 fuel pumps on this animal. One mechanical lift pump, and two in the VST: a boost pump and a high pressure pump. You're either sucking air somewhere, or the lift or boost pump is on its way out. Do you have a primer bulb on this thing? If so, it shouldn't.


Boat has had a primer bulb since I purchased and it was even replaced by BPS mechs earlier this year. I can hear the pumps in the VST "working" when I turn the key on. Where is this other pump you're referring to located. You appear to know more about this motor than I do so I will ask this. If any of these pumps are failing, would fuel & air PSI maintain through out the dyno test and a load is being put on the motor? Because the pressures never dropped during these tests.


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## Finsleft258 (Oct 7, 2018)

Answers to your questions first--The first pump is a diaphragm pump that is the primary lift pump for the engine. It is square shaped and bolts directly to the powerhead. It operates from crankcase pressure. The second pump is the boost pump. It is plumbed directly into the high pressure pump to eliminate suction losses. The latter two are both inside the VST. You will not be able to differentiate one from the other on sound alone. The engine will run with an inoperable boost pump but with the other two functioning. It will also run with a lift pump failure (or even degradation) but the other two functioning. It will run like shit at all ranges or not at all with high pressure pump failure. 

If the pumps are beginning to fail, you may seen the correct pressure but the volume is not there. Pressure drop is a blip by the way. Like, if the needle moves, AT ALL, it's fucked--replace the pump. I cannot tell you how many people miss that. 

My opinion is that you have one of the following: air leak at the separator, fuel restriction caused by unnecessary hardware (we'll come back to this one in a minute), or fuel pump failure/degradation. 

In the Opti rigging guide, fuel bulbs are not recommended--they are considered a fuel restriction. External separators are also not recommended for the same reason. The engine has a separator in the VST (red cap looking thing). While neither of those is likely to cause an issue in most applications, they can, have, and certainly do. They may also indicate a weak lift pump. Given that you have had fuel issues (water) in the past, replace the pumps in the VST if you haven't done so. 

Also, when you say he's running it on a dyno...what does that mean? Does he have a device on the propshaft? Does he have a test wheel that he uses in lieu of your propeller? If there isn't something that physically hooks to your engine to produce resistance (load) or if he doesn't use a test wheel in place of the prop when tank testing (which produces load...no a prop in a tank won't cut it), then that boat needs to be in the water for testing the fuel system.


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## Chad Cohn (Mar 8, 2018)

The dyno is used to imitate a load on the motor. Not sure of the specifics but I did ask if it did do that because you wouldn’t see the problem if there wasn’t a load. I will check the other items you mentioned as well. As far as replacing the VST pumps, due to cost I can’t do that right now. But I believe I read there’s a rebuild kit for the lift pump but I may be wrong. Thank you for explanations of this.


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## Finsleft258 (Oct 7, 2018)

Chad Cohn said:


> The dyno is used to imitate a load on the motor. Not sure of the specifics but I did ask if it did do that because you wouldn’t see the problem if there wasn’t a load. I will check the other items you mentioned as well. As far as replacing the VST pumps, due to cost I can’t do that right now. But I believe I read there’s a rebuild kit for the lift pump but I may be wrong. Thank you for explanations of this.


There is a rebuild kit for the lift pump... It's fairly inexpensive. I have a major problem with the dude not replacing, or at least recommending replacement of the boost and high pressure pump after a known water exposure to the fuel system. Water is the fastest way to nuke an electric fuel pump. If it's quick and then right back to fuel, it MAY survive. If it sits for any length of time (days, not weeks) with any amount of water in the VST, it's toast. 

The dyno deal is a bit off for me for a few reasons. They are incredibly expensive, the setup time for an outboard is not exactly quick, and they don't "imitate" load, they actually load an engine. The only outboard shops I know that have them either do product validation and testing or build race outboards. I'm not trying to knock your guy, but something's off. 

I also don't care about his experience. The most complicated outboards out there are the 425xto, any E-tec, the Seven, the Verado, and the Opti. They are all complicated for various reasons. Everything else out there is a cakewalk by comparison. You need a guy that knows Optis.


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## Chad Cohn (Mar 8, 2018)

If I recall correctly the tank was drained rather quickly after the diagnosis of water in the fuel. Again I’m super appreciative of your advice. I plan on trying to look at the pumps tomorrow after work.


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## SomaliPirate (Feb 5, 2016)

Chad Cohn said:


> So the switch appears to be good, alternator connections are good but I cleaned them anyways. Battery terminals are clean. I looked at every fuse block I could find (on the motor) and no fuses are blown. I'm still working through the connections in the console. FTR, Mako wiring is the absolute shittiest I have seen. I think rats would run from the nest that it is, so I'm trying to clean it up while I'm at it. I'm going to replace the filler hose and vent hoses tomorrow assuming I don't run out of daylight again. So far all connections I have looked at appear to be in working order and dry. Going to look at the sending unit as well and ensure everything is tight and clean. Batteries are out and I'm going to charge them individually and check the voltage on them too. I'm considering replacing the battery switch but haven't decided yet because I don't necessarily want to swap out good parts...yet. I plan on completely dismantling the boat in late Jan or Feb because there are some other issues I want to address as well so if I can get it working for the time being I'll be happy.


I don't think you've looked at Maverick wiring then...


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## lemaymiami (Feb 9, 2007)

As a guy who runs a Maverick I can't say a word.... Particularly because I'm the fool that rigged it out - all those years ago.... I may have the only Maverick they ever let go in un-rigged condition so I just go look in a mirror whenever I have accessory troubles... 

I keep threatening to hire a proper electrical type to re-wire my mess - but not sure there's anyone that would take the job (if I had the money...).

Fortunately the circuits that concern the motor are entirely separate from all the accessory stuff - so if the motor starts, runs, then shuts off when you want it too - a wiring tangle under the console probably has little to do with his motor troubles...


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## SomaliPirate (Feb 5, 2016)

lemaymiami said:


> As a guy who runs a Maverick I can't say a word.... Particularly because I'm the fool that rigged it out - all those years ago.... I may have the only Maverick they ever let go in un-rigged condition so I just go look in a mirror whenever I have accessory troubles...
> 
> I keep threatening to hire a proper electrical type to re-wire my mess - but not sure there's anyone that would take the job (if I had the money...).
> 
> Fortunately the circuits that concern the motor are entirely separate from all the accessory stuff - so if the motor starts, runs, then shuts off when you want it too - a wiring tangle under the console probably has little to do with his motor troubles...


Mine is an absolute bird's nest, but everything works so I guess I can't complain all that much. If anything major ever goes down, though I'm just going to fully rewire it. There's no way I'm going to try to isolate and diagnose anything in that mess!


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## lemaymiami (Feb 9, 2007)

What I've found over the years (I bought my skiff from the manufacturer in 1988 but it sat in my garage for two or three years until I could buy all the pieces and parts to rig it out...) is that the real difference between a rational, professional wiring set-up - and the way amateurs like me do wiring... is the troubles you get into when there's a glitch somewhere.... All my connections are solid, heat shrinked, tinned copper, etc - but it does take me twice (or three times) as long to diagnose and fix an electrical problem. I've learned to live with it over time - but it's not what I'd do today at all... I'd spend the bucks and get a pro to do the job. My other complaint is that I'll never have a mini-console ever again on any skiff I set up (if I have a choice) since the lack of room up inside is a major PITA....


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## Chad Cohn (Mar 8, 2018)

The console size is the reason alone is why I'm considering a side console. I'm 6ft tall and around 250lbs and pretty broad shoulders so trying wedge my big ass into the console to do anything is a huge PITA. So back to my boat, after some good info/advice and conversation I'm fully convinced that this isn't electrical (as in wiring). So now continues the painful process of elimination. Stay tuned but with the Xmas upon us I'm not sure how much I will get done. In the meantime I can still fish out of the boat because my local lake is small and I don't have long runs.


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## Marsh Pirate (Sep 15, 2016)

I scanned the post so if it's already been talked about, my bad. Have you checked the air compressor yet?


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## Chad Cohn (Mar 8, 2018)

It hasn't been mentioned but I did have it looked at and it's good.


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## Chad Cohn (Mar 8, 2018)

Finally happy to report that Finsleft258 was correct and fuel pumps were bad. Rebuilt lift pump and replaced boost & high pressure pumps and she runs great again.


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## Marsh Pirate (Sep 15, 2016)

Good deal, glad you got it fixed. Thanks for letting us know.


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