2003 Yamaha 75 hp
My engine is making a light coughing noise when at idol or engaged slightly while transiting threw the harbor. Once I apply the throttle to half or full power it runs fine. It has been doing this since I first bought the boat 2 years ago. It is a 4 stroke yamaha 2003 75hp. I would guess about 500 to 600 hours on the engine. New plugs and wires. Any suggestions on what it might the cause of the noise?
if it is backfiring at low speed, the idle jet is probably set too lean. might be set from the factory, or prior owner for a different altitude. have the local shop rejet it for your altitude.
Last edited by dayooper; 05-26-2011 at 07:14.
Reason: gotta learn to spell!