1988 Yamaha 130

[hunter1339]

Just put two carbs on the starboard engine. The engines needed them. But now I have a new problem, At idle the engine is steady but when I raise it a little at a time and I get to 2400 rpm she starts [racing on her own]then coming back down, she fluctuates from 2440 to 5000 rpm NOT under load. And she almost sounds like she is missing.,But ,under load she does not demonstrate any of the problems mentioned above. Note: On a car engine I raise the rpm to 2000 and hold it there to insure the engine is not breaking up at higher RPM.

SINCE 2010 I HAVE REPLACED THE GAS TANK ALL FUEL LINES AND FILTERS. MAJOR TUNE UP WATER PUMPS, THERMOSTATS.

I REPLACED THE CARBS ON THE PORT ENGINE AND NO PROBLEMS

ANY IDEAS WOULD BE APPRECIATED.

Found the problem, BAD Fuel. So while everyone was worried about proper diction I tested the fuel and fixed the problem which also caused the engine to rev up and down on IT'S OWN. So much for forums

[rodbolt17]

quit revving the engine with no load.
not only is it useless it can damage the crank rodjournal surfaces.
if it runs ok under a load all is well.

[hunter1339]

1988 Yamaha 130

I am not reving the engine, it is doing this by itself. Thanks for your advice. I figured if it idled with no problem it was OK.

[99yam40]

At idle the engine is steady but when I raise it a little at a time and I get to 2400 rpm she starts racing
,But ,under load she does not demonstrate any of the problems mentioned above

Sounds like you are revving it with no load from what you wrote