200hp 2 stroke revs dying...

[MakoJohn]

I have twin 200hp 2 stroke carbureted Yamahas on the back of a Mako 261. Both engines normally rev to 5200 but the starboard motor is playing up. Won't rev past 3500 and then rpm dies off to circa 2000 after a minuted or two I can rev it to say 3000 and then it dies off again to 2000.

I removed the fuel priming bulb thinking it may be causing a blockage and the engine ran at 4000rpm for 10 minutes before dying off to 2000 again.

Does this sound like a fuel or electrical issue? Clues? Input much appreciated?

John

[rodbolt17]

my guess is fuel.
find the issue before you get to post about detonated pistons.
could be a restriction.
could be an air leak,
could be a bad fuel pump.
could be debris in the fuel bowls.
you pick.