The current problem is that the drive will not fully engage when placed in reverse. There is a noticeable clunking noise that sounds like gear teeth slipping or jumping. Forward and nuetral are working, without such a noise. The only two changes I've made this year are a new prop, and changed the lower unit lube. I don't know what lube was in the unit prior to this. I replaced the old lube with the required type "C". The old lube was noticeably "thicker" than the new type "C". When this problem first happened a week ago, I pulled the boat out of the water and checked the unit's lube level and condition. The color and clarity seemed fine. I drained it again as a precaution, and didn't notice any metal debris or other contaminants. I then filled the unit until it flowed from the vent hole (replaced plugs of course). I put the boat back in the water and had the same trouble. As for the prop...I have had this motor for two years. I bought a 13.5x15 three blade, based on the recommendation of a local service shop. When the boat is moving in forward gear, it gets up on plane easily, and runs in the upper 26-28mph. I don't have a tach to judge the RPM (I understand this is important for optimum performance). Is it possible that these changes could affect my current problem, or did I just finally wear out the reverse drive gear? What should my next troubleshooting process be? The total time on the water with these changes is only about 20mins!
