black max 150 trouble

[Blue_Runner]

Willy,

I'm surprised I haven't heard anybody mention this but, have you checked the spark plugs?

My Yamaha 150 was fouling spark plugs right before I repowered with a new motor. Sounds awful similar to your problem. If you take the plugs out you should be able to tell which ones are causing the problem.

Another thing, once a plug was fouled, it would sometimes un-foul (if that's a word). In other words, I could go along just fine, then the plug would foul and I couldn't get over say 2500 RPMs. Then it would kick back in and run normal for a while. Sometimes more than one plug would foul and I couldn't even get to 2000 RPM. It was easy to tell what was happening cause after installing new plugs it ran great. Plus after pulling the plugs you could tell which ones were fouled.

Seems like a simple thing to check if you haven't already.

Good luck!