Sudden RPM Loss?

[Skools Out]

I had a 120 doing the same thing and it was just a bad plug somewhere they all showed fire. I went threw that motor over and over finally put a new set of plugs in the motor out of a known good running motor and that fixed the problem. I'd try a new set of plugs first off. Actually do a compression test if all good go to the plugs. the set i threw away from the 120 were new only had the boat out once and it did that so new is not always good.