I just put this motor, J120TXCEM on a boat I just bought. Motor starts on first revolution, idles ok and sounds like it's missing up to about 3800-4000 rpm then takes off. Once on plane and at 4200 rpm the rpms and speed will increase, usually to 5000 rpm. I have to be attentive to the throttle because the motor will gradually rev up and down. The motor sat for over a year and maybe two. Prior to starting motor I removed all old gas from tank and cleaned the tank, drained the car bowls and ran clean gas through them, replaced all fuel lines and filters and had to replace a powerpack. The plugs had a black coating on them, compression is 115-118 on all cylinders. I have not adjusted timing etc. I bought the motor will controls that were set up on another boat and just left everything as it was.
After the first run and having the missing I replaced the plugs with QL77JC4 which is what the manual calls for, but with no change, these plugs come out a little wet. The plugs that were in there were L82YC. Should I go back to the original plugs or does this sound like a fuel problem. Thanks, John
After the first run and having the missing I replaced the plugs with QL77JC4 which is what the manual calls for, but with no change, these plugs come out a little wet. The plugs that were in there were L82YC. Should I go back to the original plugs or does this sound like a fuel problem. Thanks, John