2002 50 hp 4 stroke surges

[terrymadtown]

Hi
I have a 2002 Johnson 50 hp 4 stroke that the engine rpm surges up and down and the engine starts to shake when the RPMs go over 2500. I have replace the prop with a new one of the same size and pitch but it did not help. Where should I go from here?
Thank you.

 

[goldstem]

Re: 2002 50 hp 4 stroke surges

replace the spark plugs. we had that exact same engine (it's actually a suzuki) and had that exact same problem. new plugs (and the old ones looked okay visually) and it ran great.
Suzuki calls for new plugs every 200 hours or so, ours acted up at 300 hours.