Low RPM in full throttle and engine revs up in neutral

[CoraDiver]

Bought a used 1993 90 HP two stroke yamaha that has been in storage for some time now. I took the boat out today and noticed that the motor was running very slow even in wide open throttle. When I put the motor in neutral I can hear the motor reving up as if I was increasing the throttle. Does anyone know what might be causing this?

Also, I can hear a very bad grinding noise when I put the motor in reverse. I suspect this may be a sign of a bad gear case but does that contribute to the problems mentioned above?

[rejesterd]

I would drain the lower unit and look for metal flakes in the oil that comes out. If you see bits of metal, then you probably need to open it up and see which gear needs replacing.

It could be the related to the low-speed-at-WOT issue, but I would fix the lower unit first regardless. Then if it's still slow after that, try treating the fuel with a full bottle of SeaFoam or something similar, and maybe spray some carb cleaner in the air intake.

[99yam40]

time to look at the controls.
shift and throttle to make sure they are set properly.

when shifting into reverse it sound like it is not making it all of the way and you are hearing the clutch dogs not fully engaging.

on the revving by itself in neutral.
see if throttle linkage is binding up and opening up by itself when put in neutral

[ausnoelm]

I would drain the lower unit and look for metal flakes in the oil that comes out. If you see bits of metal, then you probably need to open it up and see which gear needs replacing.

It could be the related to the low-speed-at-WOT issue, but I would fix the lower unit first regardless. Then if it's still slow after that, try treating the fuel with a full bottle of SeaFoam or something similar, and maybe spray some carb cleaner in the air intake.

What do you think spraying carb cleaner in the intake is going to achieve?? as mentioned check cable and carb adjustment first, seeing as the motor has been sitting for a while, you may need a proper carb cleaning (not a spray)