Finally got my 89 120 working great. When underway every once in a while there is a slight bang from the motor. it doesn't happen at any set RPM just randomly. Is the lower unit clutch going bad? How long until its totally shot and needs a rebuild?
Did you check the outdrive oil or change that It is recommended annually normally when winterizing. was the oil milkey or solid green oil. you may have water in the oil. have pressure tested or serviced if not sure.
I changed it recently when I got the motor running good. This was the first time I took it out for the day besides testing it for a few minutes here and there. The lu fluid was black when I replaced it. I also adjusted the shift cable because it wasn't going fully in neutral. I could hear a slight ticking when I spun the prop by hand. The lever on the motor side wasn't fully pointing down. Maybe the cable is stretched/stretching out. It goes in neutral now fully.
Should I check the fluid again?
Should I pull the LU and check the shift rod height?
The random bang like you hit something is characteristic of a worn clutch dog/forward gear. Improper shift adjustments certainly will contribute to premature wear. But once it is worn, there is no way to restore it other than parts replacement. And every time it bangs, the wear greatly increases. The banging also can damage the shifting mechanism.
I adjusted the shift rod to the recommended height of 21 15/16. When I first removed it and measured It It was in forward so I don't kn ow what it was originally. I didn't realize that when re-installing the lower unit the shift rod would spin. I did two trips on it since I adjusted it. One in the ocean in some decent surf and another to dive somewhere about 10 miles away with two other people. It hasn't banged yet. I hope it holds for a while. I picked up a used lower unit on Craig s list for cheap as a back up.