1996 30hp yamaha 3 cylinder 2 stroke no power

seanross

Cadet
Joined
Jul 19, 2009
Messages
18
hi, i have a 6j8 30mlhu yamaha 3 cylinder 3 carb 30hp 2 stroke. idles great, starts great, runs great.... until it gets to wide open throttle. it seems like its losing a cylinder. then when you back off the throttle it gains power for a split second then bogs again. i have had the carbs off several times and no luck or change, fuel filter tank and lines are all clean. i bought the motor not running. needles were stuck in the seats (i know). and also installed new head gasket, impeller, and plugs. i have never been able to get it to work good at WOT. any ideas? there are adjusting screws on the carbs that are not for idle so i assumer air/fuel mix. anyone know what these should be set at? any help would be apreciated thanks.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
9,119
Re: 1996 30hp yamaha 3 cylinder 2 stroke no power

Sounds like you really need to pick up a manual for your motor.
Look in the frequently asked question part of the forum and test the fuel supply system to make sure it is functioning properly and not sucking air.
 

timster

Seaman Apprentice
Joined
May 22, 2010
Messages
37
Re: 1996 30hp yamaha 3 cylinder 2 stroke no power

Does it sound like it drops a cylinder at wot ( running rough) or does it just not seem like its running WOT but running smooth? My brother in laws boat has a similar issue. The throttle linkage is messed up on it and won't let it run full throttle. Actually if you leave the throttle wide open after a while it will get slower and slower and you have to pull back the throttle and then floor it again. It does like your saying though, as you pull back on the throttle at some point it will speed up some.
 
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