1993 55hp Evinrude runs rough at high RPM

Hello everybody, I'm new to this forum and just hope to get some help. I have a 93 2stroke Evinrude 55hp. It starts up and idles and runs at low rpm very well. Once it hits probably about half max rpm is runs very rough and shakes and bucks bad and loses power. I've seen several posts about the s.l.o.w mode and this seems like exactly what the problem is but there isn't a brown wire leading to the cylinder head like they talk about. I can give full throttle and it runs great until it gets to this specific RPM, probably around 2500? It does the same if I bring it up slowly and it is very sudden, not gradual at all and I know it is a specific RPM, not throttle position. I have replaced the power pack and ignition coil so I know this brown wire doesn't exist on this model. Also replaced spark plugs and cleaned the carbs and jets. Fuel and pump is new and filter is clean. Also, pulled the choke when this symptom hits and it doesn't change anything so I really don't think its fuel. Anyway, sorry this is so long but I just want to put all the information out there. Please help

Re: 1993 55hp Evinrude runs rough at high RPM

I think there is a "sensor assembly", i think under the flywheel. What does this sensor do exactly? If this sensor is bad, will it cause the s.l.o.w mode?

Re: 1993 55hp Evinrude runs rough at high RPM

Ok so I also forgot to mention that there is a jet lower unit. I confirmed with an Evinrude tech that it is the correct one but I am hitting the rev limiter, not the slow function. I dont want to spend the money on the power pack with a higher rev limiter, does anybody know which wire I can cut to disable it?

Re: 1993 55hp Evinrude runs rough at high RPM

Ok, mystery solved. The problem the whole time was cavitation, which caused the engine to over rev and hit the rev limiter. The cavitation was caused by a bad impeller and sleeve and being mounted wrong so the angle was not good enough to pick up enough water. I am not the greatest mechanic in the world, as is obvious, but it sure was fun doing what I could and learning a lot and it sure feels great to finally have it up and running. I kinda feel like I'm talking to myself but thank you to everyone who read. Fair winds and following seas