# Yamaha 2 stroke missing



## southerncannuck (Jun 27, 2016)

It’s a 1997 Yamaha C60 two stroke. When it’s run for the first time of the day it will not run at full power. It idles fine but when the throttle is advanced it only produces partial power. This lasts for about a mile then it runs perfect.
We toggled the choke to see if that might clear something in one of the carbs but that didn’t help.
We changed the plugs and that didn’t help....but after running it a bit we pulled them out and the bottom one was very clean. Still looked new with very minor signs of ignition. The other two looked normal. A little sooty.
So we suspected a coil and replaced the associated coil. No look luck.
Anyone have any suggestions?


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## flfishpace (Aug 12, 2020)

southerncannuck said:


> It’s a 1997 Yamaha C60 two stroke. When it’s run for the first time of the day it will not run at full power. It idles fine but when the throttle is advanced it only produces partial power. This lasts for about a mile then it runs perfect.
> We toggled the choke to see if that might clear something in one of the carbs but that didn’t help.
> We changed the plugs and that didn’t help....but after running it a bit we pulled them out and the bottom one was very clean. Still looked new with very minor signs of ignition. The other two looked normal. A little sooty.
> So we suspected a coil and replaced the associated coil. No look luck.
> Anyone have any suggestions?


I would try replacing the fuel filter as I had the same issues and that was the culprit.


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## southerncannuck (Jun 27, 2016)

flfishpace said:


> I would try replacing the fuel filter as I had the same issues and that was the culprit.


I forgot to mention that we did change the fuel filter.


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## Smackdaddy53 (Dec 31, 2012)

Make sure your batteries are charged up and the leads are solid including connections at the terminals and all links.


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## Surffshr (Dec 28, 2017)

I’m following as the last time out I had a similar issue with mine. Didn’t take a mile for it to catch, but more of a boooooooooooooog-boom! Thingy.


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## southerncannuck (Jun 27, 2016)

Surffshr said:


> I’m following as the last time out I had a similar issue with mine. Didn’t take a mile for it to catch, but more of a boooooooooooooog-boom! Thingy.


I’m hoping some of the mechanical heavy hitters chime in.


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## Smackdaddy53 (Dec 31, 2012)

southerncannuck said:


> I’m hoping some of the mechanical heavy hitters chime in.


I’m just a dude that rebuilds diesel engines and does all my Yamaha 2 stroke engine work, boat rigging and has just designed a low water pickup system. I don’t know what you mean by a heavy hitter. JC Designs is a certified Yamaha tech.


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## southerncannuck (Jun 27, 2016)

Smackdaddy53 said:


> I’m just a dude that rebuilds diesel engines and does all my Yamaha 2 stroke engine work, boat rigging and has just designed a low water pickup system. I don’t know what you mean by a heavy hitter. JC Designs is a certified Yamaha tech.


I very much appreciate your help. That’s what makes this site so valuable.


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## Mark H (Nov 22, 2016)

Whole thread is good news. I initially thought someone's outboard had been stolen.


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## JC Designs (Apr 5, 2020)

I believe the fuel pump pulse come from number 3cyl. I am guessing a bad fuel pump diaphragm flooding the cylinder is causing it to not light up until enough air is introduced to clear the excess fuel.


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## Surffshr (Dec 28, 2017)

So a clean #3 plug may indicate this?


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## southerncannuck (Jun 27, 2016)

JC Designs said:


> I believe the fuel pump pulse come from number 3cyl. I am guessing a bad fuel pump diaphragm flooding the cylinder is causing it to not light up until enough air is introduced to clear the excess fuel.


That’s awesome. I’ll replace that and let you know. (Do you like Irish whiskey?)


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## JC Designs (Apr 5, 2020)

southerncannuck said:


> That’s awesome. I’ll replace that and let you know. (Do you like Irish whiskey?)


I have always recommended a fuel pump replacement every other year needed or not to prevent mishaps. Keep in mind, this is also your oil delivery. 

I am a bit on the Irish side!😉 More of a “cheap” bourbon aka Beam drinker though lol.


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## JC Designs (Apr 5, 2020)

Surffshr said:


> So a clean #3 plug may indicate this?


Yes. If not firing then no color will set. Also, if the pump is dumping fuel then any color that the plug built up during combustion gets washed off when throttle plates close again.


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## southerncannuck (Jun 27, 2016)

JC Designs said:


> Yes. If not firing then no color will set. Also, if the pump is dumping fuel then any color that the plug built up during combustion gets washed off when throttle plates close again.


Fuel pump assembly is on order. We’ll let you know.


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