Coupling walking off shaft 1995 2000flsm

[silvermw]

Recently changed out my strut bearings as they were worn. Cleaned up the coupling with some emery re installed coupling with key and tightened set screw onto shaft yet the coupling seems to be walking off the shaft. Set screw will not stay tight. Any ideas on what’s happening and how to fix

[boatwakes]

IIRC the shaft coupling is aluminum on those years and easily deforms. Furthermore, those shafts are not double taper (tapered at the coupling side as well as the prop) and pretty much utilize the woodruff key to carry the torque from the engine to turn the prop. You're eventually going to snap the shaft at the keyway because of the coupler problem. There are two ways to get it to work and one way to repair it correctly.

1) The right way to repair this situation is to replace the shaft and coupler with a double taper from Elgin's. I wrote a post on it somewhere here and if you search for it, it should be buried in the last 6 months or so. Total cost about $500 with your labor. New shaft comes with fit and faced coupler and keys but requires some measurements on you part. This is the HIGHLY RECOMMENDED SOLUTION and will provide a lifetime of serviceability. Be sure to read the propeller lapping and alignment procedure as well.

2) You can also replace the coupler but I don't recommend this option because again, the key and keyway have been taking the torque instead of the shaft taper.

The key is micro-shifting during use and causing the set screw to back out from tiny vibrations. You can use loctite on the set screw BUT THIS IS NOT THE PROPER SOLUTION TO THE UNDERLYING PROBLEM.