I have a 1975 135 hp Johnson. Carbs are completely clean, and compression is perfect. However, at idle, she sometimes cooperates and sometimes doesn't. I run the standard johnson outboard oil, $17/gallon, and think this may be to blame.

Do you think if I ran the synthetic stuff...I just read you can buy the synthetic stuff from GI Joes for $20/gallon that it will not foul the plugs. Also, what does it mean to run a hotter plug? Right now, I just have the standard champion plug.

Thanks in advance for any input.