25hp Johnson cylinder issue

[Tommy2988]

I have a 1997 Johnson 25hp. The issue is I'm running weak on one cylinder. So far I've rebuilt carb. Verified good spark. Even swap coils to see if the problem would move. I've set all the linkages and timing by the book. It's the bottom cylinder if that matters. Compression is 120 and 119. Doesn't backfire or spit. Plugs are wetter than what I would say is normal. Could it possibly be a Reed issue? There's no broken or excessive bent fins on them from what I can see looking down the intake throat. Buddy said replaced the cdi box. I feel like swapping coils would have eliminated that.

 

[flyingscott]

How did you verify spark? It needs to jump a 7/16" air gap.

 

[racerone]

Did this issue develop suddenly ?----How did it run last year ?----Checked the fuel pump diaphragm ?-----Could be a bottom crankshaft seal issue as well.

 

[Tommy2988]

I bought the already like this. I did notice the other day in the river if I'd go from full to zero back to full throttle. The motor would try to catch on the second cylinder. But as of yesterday I couldn't get it to duplicate the problem. I had a buddy turn the engine over while hold the plug at least an inch from boat and it'd easily clear the gap with a solid blue strike.

 

[oldboat1]

could be inconsistent spark. I would start simple, and either replace plug wires or clean and refurbish them.