While using my 2000 Yamaha T9.9exry last year the RPMs would drop and the motor would almost die and then about 60 seconds later the RPMs would pop back up. I was running the motor at about 3/4 throttle. And this would happen about every two minutes. This motor is my primary motor on my 30 ft trimaran. I felt that this was most likely a fuel problem but my dealer here in town told me that it was fouled spark plugs because at the time I was not using a thermostat (while I was waiting for it to come in the mail.) I have since rebuilt the carb, fuel, pump, and lower end but I still don't trust my motor being that I'm not truly sure I have fixed the problem. I would like to avoid having to buy a new motor before I feel safe using my boat again. If any one has ever had similar problems or helpful thoughts your input would be very helpful. Thanks in advance.
