1997 Yamaha 25hp will not make power and has problem idling

Hi everyone. I have a 1997 25hp, 3 carb, on a 16ft aluminum skiff. My problem is that it will not develop any power to go anywhere. When it runs great, rather before my brother loaned it out, it would run like a top at full throttle, clocking out around 32-34 mph. Now, I barely do 6 mph and cannot plane out of the water, at full throttle. It sounds like it is stuck a certain RPM and can not go past that, WOT or not.

My first suspect was the carbs, I have had some problems with them and the jets getting clogged. I took them down and they were very clean. Fuel filter was clean. Nothing was leaking. Throttle cable was good, it moves the throttle plates as they should. Spark plugs were recently changed in January, and look good. Would anyone have an idea on the next place to check? My gut tells me the little black ignition box may have something to do with my problems. How would that be checked, if it could be bad? Could it be the carb adjustment out of spec?

Re: 1997 Yamaha 25hp will not make power and has problem idling

Check compression to start out with to see if the motor is still a good motor.
If some one ran it with fuel restriction it could have ate a piston or 2.
Then check spark, timing,and fuel pressure/vacuum to see if they are in spec

Re: 1997 Yamaha 25hp will not make power and has problem idling

99yam40,

Sorry for the late reply, got shipped offshore for a quick tour. I'll check the compression on all of the cylinders, what would be some good numbers to see on this test? Where would be a good place to get a manual, I would think that they would have a section to do diagnostic tests on these motors. Thanks for your help!

Re: 1997 Yamaha 25hp will not make power and has problem idling

No spec on compression but I would think about 100-120 as long as all 3 are close.

Might check timing to make sure it is advancing properly also