yamaha 90 2 stroke problem

D

daver034

Recruit
Joined
May 16, 2011
Messages
3
I have a yamaha 90 2 stroke with 125 hours on it and the engine runs great from 0 to 32 mph, but when i try to get more out of it it loses power. It will run 32 mph all day! I have changed the spark plugs and the fuel filter and have tried some gas remedies, Does anyone have any ideas, Thank you.
 
N

noelm

Senior Chief Petty Officer
Joined
Mar 8, 2005
Messages
761
Re: yamaha 90 2 stroke problem

we need a bit more info, does the motor miss at high speed, or just does not go any further? what exactly is "gas remedies" was it OK before? do you have a genuine service manual?
 
D

daver034

Recruit
Joined
May 16, 2011
Messages
3
Re: yamaha 90 2 stroke problem

when I throttle up toward the max the motor losses power and I have to slow the boat down and throttle back up again. I tried sea foam, yahmalube, and sentry treatment. Tried these thinking maybe thing was stuck in the carb or gas. It has been doing this since I got it before the gas treatments. Also I having only been using E free gas . Thanks
 
D

daver034

Recruit
Joined
May 16, 2011
Messages
3
Re: yamaha 90 2 stroke problem

key west 1720 center console and a ss prop. Thanks
 
9

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,878
Re: yamaha 90 2 stroke problem

It is best to test everything that you can and then work on the things you can not test if the problem has not been found, like the carbs.

Compression, spark, timing, and fuel delivery system are all easy to test. Here is a good post on the fuel system. http://forums.iboats.com/showthread.php?t=283363


Fuel additives are not a way to clean carbs they need to be taken apart and cleaned properly, and then adjusted like the service manual states.

Could you have a set up problem?
Easy to test to see if the motor has a problem with making the proper HP at RPM with a test prop that your Yamaha shop should have.
 
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