T&T: Results of shaft couplers inspection

[Rich Gano]

I reported problems with my shaft couplers discovered in late August while
testing a transmission repair.  The shaft couplers I had were simple,
non-tapered style (meaning no holding nut on the front end of the shaft)
with set screws located 180 degrees apart rather than a more secure 60-90
degrees apart.  A key was also incorporated into the design.

The transmission repair mechanic discovered that whenever the transmissions
were placed in reverse, the shafts and keys would back out of the couplers
up to about a quarter inch.  Placing the transmissions in ahead gear pushed
the shafts and keys right back into place.  Nothing I could do in the way of
tightening or replacing the set screws would resolve the backing-out
problem.

We finally caught a break in the busy haul-out schedule and got the boat on
the hard on 22nd of September.  After blasting the hull and moving the boat
to its work stand, we finally got the shafts pulled.  As I suspected the set
screws had obviously been set into dimples, and there had been enough
looseness somehow that the screws worked elongated grooves along the
longitudinal axis of the shaft.  Unrepaired, the eventual result would have
been the keys dropping out and/or the shafts backing out altogether.

I have opted for the longest Buck Algonquin split couplers available for
this size shaft, and have sent off the shafts to a machine shop for fitting.
The practice here is to put a pin through the shafts and couplers at the
front end of the split such that tightening the clamping bolts holds the
pins in place.

A neighbor who in the past has been a yacht broker noted that he has seen
the unsatisfactory shaft couplers I am getting rid of in a lot of new boats.
Again, I urge everybody, regardless of couplers owned, to observe their
shaft/coupler interaction when backing on a regular basis.

Rich Gano
CALYPSO (GB-42 #295)
Southport, FL