I'm new to this bulletin, and am looking for some advice to help me solve a yamaha outboard mystery. Own a pair of 1989 130 yammys. These motors push a 21 foot power cat and after warming up, the starboard engine will run at full throttle (5500 rpms) for 10-30 seconds at which point it suddenly fluctuates across the entire power curve and quickly looses power to the point of stalling. Afterwards I am able to start it up and idle around the harbor but when I accelerate to full throttle it exhibits the exact same behavior. I have had both yamaha mechanics and other outboard mechanics run the motor on the beach through the entire rpm range with plenty of warm up time and no trouble. One mechanic thought there was debris in the carbs/fuel lines and competely dissembled the carbs, cleaned them out, and ran high pressure air through the fuel lines and carbs which changed nothing. The yamaha mechanic diagnosed the problem electrical and replaced the stator, again not fixing the problem. I have replaced the fuel filter on the outboard and my primary fuel filter, and use 3/8" fuel hose to ensure plenty of fuel. Now the yamaha mechanic suspects the problem lies in the charging coil and wants to replace it as well. I kind of suspect an electrical problem as well, possibly related to temperature and load, but am getting tired of funding this seemigly allusive fishing expedition. Any suggestions? Please advise, thanks for any help.
