86 yamaha 200 hp question

brianmccaw · #1 04-08-2009, 02:02 PM

Hey all,
I have an 86v with an 86 yamaha 200hp precision blend outboard. Under WOT the engine sounds and runs perfectly fine. However, while at a slow idle as i increase the power the engine begins to run roughly and vibrate throughout the rpm range until i get to almost full power. All the plugs were changed and i checked for water in the gas tank. Anyone have any idea what this could be???

Monkey Butler · #2 04-09-2009, 10:14 AM

What do your plugs look like? Big difference between banks?

Are you sure that your pilot screws on the carb are adjusted correctly? On many models the settings are different for port and starboard.

After that I'd probably pull the carbs and clean them and then if the problem was still there check/rebuild the fuel pumps.

That's all cheap stuff to do.

That motor doesn't have the computerized ignition (YMIS) correct?

Steve P.