Prop shaft coupling spins but prop shaft does not. 72 E27.

Alan Gomes said:

So glad your prop shaft did not slide out of the boat and put you on the bottom! Great that you caught it when you did.

Click to expand...

That actually dawned on me at some point, that bad things could have happened. Was backing into the dock after a run, when it let go.

Perhaps thats the actual reason for the short prop shaft key...so it disengages before the shaft backs all the way out?

Going to change the water pump impeller since I have good access to it at this time. Its on the back of the motor.

Ran into a problem after placing a parts order from Moyer Marine.

The original coupling is 3/4" opening for the shaft. Repeatedly measured, of this I'm sure.

The key that it uses is 1/4" square rod.

I know this because I bought a 3/16" key and it was too small.
Swapped the 3/16" key for a 1/4" key and the 1/4" key fits perfect.

The coupling I bought from Moyer that is 3/4" only comes with a 3/16" keyway.
Called them and cancelled the order this morning.

Anybody knows where I can find an A4 coupling as per above picture for 3/4" shaft using a 1/4" keyway?
Old part is reusable if necessary but I'd rather replace it.

I don't have an answer to your specific question, but you might consider a new shaft too just to get it all fitted to the proper tolerances, proper keyway size etc. Small price to pay for a critical system on the boat. Just a thought.

Ok, I'm an idiot.

Was about to post a photo showing the size of the hole in the coupling, that it was 3/4".


The only problem is that I'm using a printed ruler and I didn't start at zero. Started at the edge of the paper.
Starting at zero, the coupling hole is 7/8".

The Moyer part for a 7/8" shaft DOES include a 1/4" keyway.
I'll go back to my closet now.


:-(

A-4 coupler 3/4" shaft 14" key way.

I have one if you still need it. Meant to be 1/4" key way. Never mind, it turns out my memory is wrong. The coupling I have is for a 1" shaft.

It can be a slippery slope... when I ordered up a new prop, I ended up needing to replace everything back to the engine.

Replaced badly worn water pump impeller.
Reinstalled the original coupling and original shaft key.
Tied the pinch bolt down with heavy copper wire so it can't back out.
Got the engine back in place but have a few bolts that don't line up with their holes.
Fixable, just called it a day.

Follow up.

All floor engine bolts back in place. Everything reattached.
installed pertronix ignition kit.
Engine cranks and runs well.
Trans works fwd and reverse.

On to the next issue.