When out sailing, I fired up the motor to return to the slip. The motor seemed like it was laboring and wouldn’t rev past 2000 RPM. Normally redline is about 3700. The engine lugged and within minutes It wouldn’t rev at all. It was stuck at 1000 RPM. I put it into neutral to see if it was something wrapped around the prop and it was the same. Wouldn’t rev. I also got black smoke. I looked up things on the internet and the service manual and the things to test were a clogged air filter or exhaust elbow. I removed the filter, cleaned it, reinstalled it and zero difference. The next thing was to check was a clogged exhaust elbow. I removed the elbow from the engine and looked inside. Poked it a bit with the screwdriver. Reinstalled and the engine idled better. No smoke at idle like before. Tried to rev the engine and it revved to about 2500. This is progress. It may not be completely fixed but maybe I have a clue as to whats wrong.