84 Johnson 35 timing problem

[venator66]

I have an 84 Johnson 35 that has begun to run rough. It was running fine when I shut it down. I started it five minutes later, and it would bog down when I accelerated but run fine at wot after working the throttle up. I put a timing light on it this evening and the timing was moving all over the place to the point I couldn't see the timing marks at times.
What would cause the timing jumping around so much and where should I start?

 

[jimdd810]

Re: 84 Johnson 35 timing problem

The rough running condition will cause the timing marks to jump around. I would start with cleaning and overhauling the carb. Also do a compression test.