bought a motor, works but not very well at high speed

[hollowjacket]

Its a Yamaha 9.9sf 6G9 S 005625 F Thats what is on the metal tag
It starts fine and idles nicely, very quiet, goes very nice at low speed, *****ing, moderate speed, but when it gets to the fast speed, it goes for a few seconds then bogs for a second and stays at a medium speed, every now and then it goes fast for a few seconds but always back to the medium speed. any advice?? I thought, maybe a carb rebuild kit, but I cant find one anywhere. someone mentioned that I should adjust the carburetor but I have no idea how to do that.

[99yam40]

test what you can to start out with.
need to know condition of motor.
compression, spark, timing, fuel pressure.
check fuel pump for leaks too.

spark, timing, and fuel pressure can be monitored while problem is happening too to see it is changing
Is there a T or F in front of the 9.9 or is this a 2 stroke motor

[hollowjacket]

oh ya, compression is good an both cylinders, it is a 4 stroke, brand new plugs spark nicely, almost a full quarter inch each, no leaks anywhere on the motor itself, pressure? dunno, but when I disconnect hose it spurts out really hard and steady.

[TownsendsFJR1300]

What year engine(if known) and is it indeed carberated?

Sounding like the carb has some clogging issues.

You don't necessarily need a rebuild kit but would have to get into the carb (with some knowledge) and clean it.


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