# 1988 YAMAHA 25hp 2 Carbs popping WOT.



## RunningOnEmpty (Jun 20, 2015)

I was going to say fuel pump, but then read it has been rebuilt. Maybe a coil is bad or one of the grounds? Sounds like a tough one to figure out!


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## redfish12 (Jan 15, 2013)

RunningOnEmpty said:


> I was going to say fuel pump, but then read it has been rebuilt. Maybe a coil is bad or one of the grounds? Sounds like a tough one to figure out!


We are going to check out the coils today for a short wire or ground and recheck the Fuel filter, fuel line/bulb. We will let you know how it go's. Thanks


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## RunningOnEmpty (Jun 20, 2015)

My Yamaha 30hp had a fuel pump problem that only effected wot. It would run strong until the carbs ran dry and it would slow down like it was in limp mode until the pump could re fill the carb bowls. I ran it wot while squeezing the primer bulb and it ran fine. That explained why the limp mode alarm wasn't going off. I honestly thought it was going into limp mode, but I was wrong.


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## redfish12 (Jan 15, 2013)

RunningOnEmpty said:


> My Yamaha 30hp had a fuel pump problem that only effected wot. It would run strong until the carbs ran dry and it would slow down like it was in limp mode until the pump could re fill the carb bowls. I ran it wot while squeezing the primer bulb and it ran fine. That explained why the limp mode alarm wasn't going off. I honestly thought it was going into limp mode, but I was wrong.


I will do the primer bulb squeez today too thanks ROE


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## No Bait / Lures Only (Apr 10, 2011)

redfish12 said:


> I will do the primer bulb squeez today too thanks ROE


My 25 Yamaha 2 cyl 2 stroke is doing the same thing except, after a few minutes of hesitation it clears out and runs wot great. Changed complete gas hose/bulb/filters/orings/ connections/tank pickup. Any ideas ?


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## redfish12 (Jan 15, 2013)

stephenchurch said:


> My 25 Yamaha 2 cyl 2 stroke is doing the same thing except, after a few minutes of hesitation it clears out and runs wot great. Changed complete gas hose/bulb/filters/orings/ connections/tank pickup. Any ideas ?


We are finding out that it might be one of the two pulse coil. Under the fly wheel. Still working on it. We do a continuity test on the coil when it's cold and it shows good but once it warms up it shows bad. It's like chasing a ghost it's there and then it's not.


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## No Bait / Lures Only (Apr 10, 2011)

redfish12 said:


> We are finding out that it might be one of the two pulse coil. Under the fly wheel. Still working on it. We do a continuity test on the coil when it's cold and it shows good but once it warms up it shows bad. It's like chasing a ghost it's there and then it's not.


Thanks, will check out coils and the diphram......


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## redfish12 (Jan 15, 2013)

We are still working on the motor WTFudge. We are now looking at a ground wire from the CDI to the motor block it was a little rusty at the block. Cleaned it up. But more important we are looking at the rev illuminator. At the lake test we notices that the rpm was 5400 at 3/4 throttle and after WOT it started to shudder, pop, miss and hesitate . On the boat and motor I have a 10 pitch prop on a 14' john boat that weighs about 120 pounds and me weighing at 170lbs and the gas at 50lbs the grand total of 340lbs. I am picking up a 12 pitch prop on Sunday and Lake test on Monday hope it work's out????


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## No Bait / Lures Only (Apr 10, 2011)

redfish12 said:


> We are still working on the motor WTFudge. We are now looking at a ground wire from the CDI to the motor block it was a little rusty at the block. Cleaned it up. But more important we are looking at the rev illuminator. At the lake test we notices that the rpm was 5400 at 3/4 throttle and after WOT it started to shudder, pop, miss and hesitate . On the boat and motor I have a 10 pitch prop on a 14' john boat that weighs about 120 pounds and me weighing at 170lbs and the gas at 50lbs the grand total of 340lbs. I am picking up a 12 pitch prop on Sunday and Lake test on Monday hope it work's out????


5400 @ 3/4 throttle so WOT must be like 6500-6800, then the rev limiter kicks in, similar to my 25 with the Turbo Hot Shot 12"


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## RunningOnEmpty (Jun 20, 2015)

You definitely need more pitch. Your boat is very light!


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## No Bait / Lures Only (Apr 10, 2011)

RunningOnEmpty said:


> You definitely need more pitch. Your boat is very light!


More pitch is the answer, my 25 runs different with 3 different props:
5850 PT SRA 12" 32-33
6800 Turbo Hot Shot 12" 33-34
5000 Solis 13" w/extra cupping 29-30


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## RunningOnEmpty (Jun 20, 2015)

stephenchurch said:


> More pitch is the answer, my 25 runs different with 3 different props:
> 5850 PT SRA 12" 32-33
> 6800 Turbo Hot Shot 12" 33-34
> 5000 Solis 13" w/extra cupping 29-30


I'm thinking about trying a Turbo hot shot. I wonder why yours turns so many rpms vs the PT SRA?


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## redfish12 (Jan 15, 2013)

RunningOnEmpty said:


> You definitely need more pitch. Your boat is very light!


Thanks l just got a 10" x 12p prop i will load up the boat and checking out on Monday


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## No Bait / Lures Only (Apr 10, 2011)

RunningOnEmpty said:


> I'm thinking about trying a Turbo hot shot. I wonder why yours turns so many rpms vs the PT SRA?


Turbo Hot Shot, it has a small amount of Rake and Cup vs the PT SRA which has lots of Rake and Cup. Also the Turbo Hot Shot will not run nearly as high as the PT SRA. PT will run and bite almost as high as the jack plate will adjust. Overall performance with the PT SRA was the best average, and PT will allow returns until you find the correct pitch.... Turbo will not.....


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## RunningOnEmpty (Jun 20, 2015)

stephenchurch said:


> Turbo Hot Shot, it has a small amount of Rake and Cup vs the PT SRA which has lots of Rake and Cup. Also the Turbo Hot Shot will not run nearly as high as the PT SRA. PT will run and bite almost as high as the jack plate will adjust. Overall performance with the PT SRA was the best average, and PT will allow returns until you find the correct pitch.... Turbo will not.....


Thanks for the tip! I was concerned the Turbo wouldn't run up high like my PT SRA.


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## redfish12 (Jan 15, 2013)

Okay we traded out the prop to a 10"X12Pitch grabs better and brought the RPM down but we still have the popping on WOT. We found out that the top cylinder is shutting down every once in a while with the WOT after warm up. My question to the marine mechanic guys. Under the fly wheel there is to pulser coil a left one and a right one. The two pulser coils under the fly wheel is one meant for the high speed timing and low speed timing or is one meant for the top cylinder and the other one for the bottom cylinder? Once again thanks for all the help and info that is coming from you all.


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## RunningOnEmpty (Jun 20, 2015)

One for each cylinder. Part is obsolete? http://www.boats.net/parts/detail/yamaha/Y-6L2-85592-F1-00.html


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## redfish12 (Jan 15, 2013)

Okay then the left one is for the top cylinder and the right is for the bottom cylinder according to the diagram showing and the info that I got from another mechanic. I did order a base assembly that I found on eBay that come with the two pulser coils and coil charger. OF COURSE it is used so I'm hoping they are in good working order. I should have them by 11/17/15. Once again thanks and I will get back to you on the 18th....


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## No Bait / Lures Only (Apr 10, 2011)

redfish12 said:


> Okay then the left one is for the top cylinder and the right is for the bottom cylinder according to the diagram showing and the info that I got from another mechanic. I did order a base assembly that I found on eBay that come with the two pulser coils and coil charger. OF COURSE it is used so I'm hoping they are in good working order. I should have them by 11/17/15. Once again thanks and I will get back to you on the 18th....


I was able to stop my 25 from popping, seems like changing the plugs and the fuel filter gasket were the issues. And now spoke to Hydrotec about the plugs fouling and it could be caused by running Mercury oil @ 50/1 vs the Yamaha lube @ 100/1, others have had the same issues as the plugs were wet and black.........


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## RunningOnEmpty (Jun 20, 2015)

stephenchurch said:


> I was able to stop my 25 from popping, seems like changing the plugs and the fuel filter gasket were the issues. And now spoke to Hydrotec about the plugs fouling and it could be caused by running Mercury oil @ 50/1 vs the Yamaha lube @ 100/1, others have had the same issues as the plugs were wet and black.........


I would never run 100/1 in a modified motor! A simple low speed fuel mixture adjustment can make the difference between fouled plugs or a good clean running motor. My Yamaha 30hp will run 40/1 and my plugs are very clean with a light tan color.


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## No Bait / Lures Only (Apr 10, 2011)

RunningOnEmpty said:


> I would never run 100/1 in a modified motor! A simple low speed fuel mixture adjustment can make the difference between fouled plugs or a good clean running motor. My Yamaha 30hp will run 40/1 and my plugs are very clean with a light tan color.


Wonder why Hydrotec told me to run 100/1 mix in the modded motor?


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## RunningOnEmpty (Jun 20, 2015)

Stephenchurch, that's a very good question? Do your own research on high revving 2 strokes and oil requirements. Maybe my plugs stay clean @ 50/1 because I'm using Amsoil HP marine? My prop doesn't even have any black oily buildup and you would think it came off of a four stroke. This is my first Yamaha and I'm really impressed with how clean it runs.


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## No Bait / Lures Only (Apr 10, 2011)

RunningOnEmpty said:


> Stephenchurch, that's a very good question? Do your own research on high revving 2 strokes and oil requirements. Maybe my plugs stay clean @ 50/1 because I'm using Amsoil HP marine? My prop doesn't even have any black oily buildup and you would think it came off of a four stroke. This is my first Yamaha and I'm really impressed with how clean it runs.


Empty, this is my second Hydrotec built engine and the 90 I had was oil injected @ 100/1 and 24 years old....I am not a mechanic, but do listen to the engine builders for directions and advice. Earlier I used to run the Amsoil in my 90, but did not gain any performance. Research, who knows more than Hydrotech and Yamaha Racing/do your own research!


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## redfish12 (Jan 15, 2013)

The wife just called me at work and told me that I received my used pulser coil parts today. I will installing the part on Monday. Soooooo lets keep our finger crossed that this will get it right.....


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## redfish12 (Jan 15, 2013)

Okay it is "FIXED" It runs like a new motor!!!!!
It turned out to be the left pulser coil that operates the top cylinder. When we tested it the coil it was cool and showed good on the omh's reading but when we heated the coil up with a heat gun it showed bad. We then purchased a used pulser coil on the ebay store from Marine Supply Inc. A good used part that was very cheap in cost. We replaced the old one with the new used one and the motor fired right up and ran great on WOT for over an hour. We shut her down let it cool down an ran it up to WOT again for another twenty minutes with no shudder, popping, miss or hesitation. Thank Goodness!!!! I learned how to test a pulser coil from the youtube channel a lot of good information in those videos.
And of course thank to all of you on the Microskiff forum for all the great information.
The total replacement parts.
1. Two new carb kits
2. One new fuel pump kit
3. New fuel lines
4. And a beautiful used Pulser Coil from Marine Supply Inc. from ebay store that got her humming again...


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## RunningOnEmpty (Jun 20, 2015)

Good job!


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## No Bait / Lures Only (Apr 10, 2011)

RunningOnEmpty said:


> Good job!


Glad to hear you finished your motor with good results


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## Dadvocate (Jun 26, 2011)

Finally fixed can we go fishing now?


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## No Bait / Lures Only (Apr 10, 2011)

RunningOnEmpty said:


> I would never run 100/1 in a modified motor! A simple low speed fuel mixture adjustment can make the difference between fouled plugs or a good clean running motor. My Yamaha 30hp will run 40/1 and my plugs are very clean with a light tan color.


Empty,
So far so good, 100/1 pre mix fuel 93 octane, motor is running great. 700# load in the 320# boat, it is topping out @ 30.3 mph gps with 200 hours on the motor. It would be hard to trade up to a 3 cylinder 40/50 engine and gain about 70# to the stern.....


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## redfish12 (Jan 15, 2013)

I'm runing Yamaha 1988 25hp 2carbs that are oil injected at 100/1 with the Merc oil and the plugs look just fine


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## RunningOnEmpty (Jun 20, 2015)

stephenchurch said:


> Empty,
> So far so good, 100/1 pre mix fuel 93 octane, motor is running great. 700# load in the 320# boat, it is topping out @ 30.3 mph gps with 200 hours on the motor. It would be hard to trade up to a 3 cylinder 40/50 engine and gain about 70# to the stern.....


Your little 25 hp is working hard! My little motor is out of commission because of the crank bearings LOL The pistons still look great and the extra oil didn't cause any ring sticking. I wonder how long my crank would have lasted with 50% less oil?


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## No Bait / Lures Only (Apr 10, 2011)

RunningOnEmpty said:


> Your little 25 hp is working hard! My little motor is out of commission because of the crank bearings LOL The pistons still look great and the extra oil didn't cause any ring sticking. I wonder how long my crank would have lasted with 50% less oil?


Empty,
Sorry about the bottom end of your motor, what crank do you need? As my close friend builds motors........


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## RunningOnEmpty (Jun 20, 2015)

stephenchurch said:


> Empty,
> Sorry about the bottom end of your motor, what crank do you need? As my close friend builds motors........


I have someone that rebuilds pressed Yamaha cranks and he quoted me a really good price. I'm still debating on buying a new powerhead? My block has seen it's share of saltwater over the years.


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## No Bait / Lures Only (Apr 10, 2011)

Keep me posted with your progress on the motor.........


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