[C320-list] Hull #894 (2002) Loose Propeller Shaft/Coupling Connection

[Robert E. Sloat]

The last time I was motoring in to my slip I noticed when going from forward to reverse and back a slight clunking sound which was a little louder that the normal sound when shifting gears.  Shifting is done correctly-at idle from neutral after a second or two, then throttle as needed.

I checked the propeller shaft coupling and discovered by holding the shaft tight and trying to rotate the coupling a little play was felt between the coupling and the propeller shaft. It was barely noticeable.  This I assumed was the cause of the clunking sound when switching from forward to reverse.  On further investigation the propeller shaft key could be slid fore and aft a little in the shaft groove.  The set screws on the coupling which go into small indentations on the shaft were not loose.  I secured the shaft and removed the safety wiring from the set screws, marked their positions and them removed them to make sure they were lined up with the dimples in the shaft for the screws to seat with the shaft.  They were.  The key was moved into the correct position so its full length was in contact with both the coupling and shaft grooves.  Then the set screws were installed and tightened a little more by screwing them in (about 1/8 more in rotation than when I took them out) but still not overly tight by my experience. The safety wiring was reinstalled just the way it was originally.

I am the original owner so there has been no removal of the set screws and the only activity on the coupling was my installation of a 5/8 inch spacer this spring in connection with a new Autoprop feathering propeller.  At that time the coupling and shaft were tight.  The Autoprop, like most 3 bladed feathering or folders is heavier than the OEM fixed 3 blade propeller it replaced and the increased inertia to be overcome when going into gear may have contributed to loosening the key, but I don't know.

So far after 5 trips in and out of the slip, when shifting gears no clunking and the shaft, key and coupling are all tightly connected.  Hopefully, this is an outlier for 320 of recent ilk.

Bob Sloat 
Savannah