Logo
FULL SITE MENU

1998 Yamaha 60 2-stroke power surging

A

a6weeks

New member
I am troubleshooting an issue with my 1998 Yamaha C60tlrw. Starts up every time runs fine in idle and at low RPMs. Im experiencing intermittent power surges when at WOT and higher RPMs. The motor never stalls out completely just seems to be affected under load. Sometimes I can run the boat for hours without experiencing an issue but it is starting to happen with more frequency. i am by no means an expert mechanic but i started with the fuels system. I have cleaned carbs, replaced fuel pump and filter. I have run the engine off an external tank and experienced the same issue so i don't believe the issue is in the fuel tank or the fuel lines. Fuel lines delivering to the carbs appear to be fine with no leaks. Also, since first experiencing the issue i have noticed the my spark plugs are fouling quickly, after probably less the 20 hours (wondering if this could be related). Any insight on where to look next would be greatly appreciated.

Alex
 
Check the compression in all cylinders. Considering the engine's age, the plug fouling, and everything you've already checked, that's where I'd be looking. I'm not sure what the spec is for minimum compression on your engine, but if you're getting anything less than 100 psi, I would say it's time to consider a new engine.
 
I know on evinrude and johnson there is a ignition box that goes to each coil and when those start to fail they’ll cause that surging your talking about. I’m not a Yamaha guy but I would think it’s similar but hopefully if the compression test doesn’t fix your problem or correct gaps on your spark plug hopefully a more experienced Yamaha guy can help you.
 
rejesterd said:
Check the compression in all cylinders. Considering the engine's age, the plug fouling, and everything you've already checked, that's where I'd be looking. I'm not sure what the spec is for minimum compression on your engine, but if you're getting anything less than 100 psi, I would say it's time to consider a new engine.
Click to expand...

Compression checked out with 125psi in all 3 cylinders
 

125 should be fine, as long as you had the throttle wide open when you did the test. So I think the main thing to focus on would be your note about the spark plugs fouling since you noticed the performance problem. Assuming the compression is ok and you installed the correct plugs, then that means it's running rich due to incorrect fuel pressure. Almost always, that means it's the carbs. I would just replace them at this point. I've heard from many people that these carbs are extremely difficult to clean and tune.

You can also try measuring the fuel pressure to see if it's higher than the expected range for that engine. If it's not too high, then start looking into all components related to ignition.
 
Hey, also on my yamaha the pump diaphragm was shot and it would pour fuel right into the crankcase and of course caused a rich condition and that would foul the plugs in no time. replaced the part and the plugs dried up and it runs fine. also check your timing. on my motor the timing was screwed up and at idle that caused foul plugs
 
Back
Top