Shaft fell out of coupling

[BreadandBoatses]

Hi,

I have been helping some friends fix their new-to-them boat and have a few questions on how best to proceed.

Their prop shaft slid out of the coupling but luckily the rudder stopped it from falling all the way out of the boat. The key was rounded, the coupling bore worn (unevenly to one side) and the keyways on the coupling and shaft worn to more of a v shape.

We wanted to see if we could rig it to work for the rest of the season until haul out to deal with properly. The coupling is a straight bore and should be an interference fit but slides freely on and off the shaft without a key. In order to fit a new key in, I had to file the keyways which had spots that mushroomed over, particularly on the shaft near where the set screw for the key had been pushed into the shaft. Even though it seems most of the wear is on the coupling (I don’t really trust my reaching one handed shaft measurements), I figure both need replacing and no sense buying a new coupling until you fix both at haul out.

The key by itself in the shaft keyway wants to knock back and forth, but with coupling on there is no wiggle room for now. I put locktite on the shaft set screws and the thing is solid for now but who knows how long.

The problem is that when I then go to reattach the coupling halves, the alignment is way off. It’s not a bent shaft because the gaps stay to the same side when I rotate the shaft. It’s so far off (like a 1/4” gap, that the motor bottoms out the motor mount slots and can’t be moved further without drilling new holes.

The misalignment could be because of the fit of the worn coupling or from the cutlass bearing. Maybe bad engine alignment was part of the original problem that led to the shaft coming out. Is there a safe way to proceed without hauling out? I imagine misalignment of that scale would be way too rough on the bearings to tolerate for the rest of the season. Should I just drill new holes for the engine mounts and align it as is or buy a relatively cheaper new coupling and see if the alignment is better or is the answer just haulout now? (For this couple’s budget by haulout now, I mean treat it as a floating dock for the first of the summer until haulout time)

(I didn’t take great photos throughout. First is from trying to fit key and second is how I found it)

[Tetepare]

Are the motor mounts shot?

[Allied39]

You obviously have multiple issues, of which most you are aware. There is no flex in that setup, flexible coupling needs to be added.
The coupling that atatches onto the shaft does not clamp, replace it with the clamping style. The style you have is fine if routine maintenance is performed.

As for when to do a proper job? Are you planning on motoring a 1/4 mile off mooring or doing some long runs. Answer that question and you have your answer.

The longer you leave this poor situation the more likely you are to do damage which will likely add to the expense of what you are going to do anyway.

Your call.

[Cheechako]

That's tough. A lot going on there to completely understand.
-Do you know if it was ever in alignment? Many are not.
-When you say off 1/4", do you mean the faces are angled to each other or do you mean just off vertically but the faces are parallel?
-For any shaft to bore non fit/ovalizing you could use brass shim stock. NAPA auto parts in many thicknesses.
-Is the rear of the engine too high or too low to mate with the shaft coupling?
-DO you realize that adjusting the front engine mounts can raise or lower the rear alignment also? Often it's a matter of adjusting front and rear until you get there... and a PITA! ie: If you lower the front mount adjustment, the tail of the engine goes up by pivoting on the rear mounts.. etc.
Need a lot more info.....

[tkeithlu]

Ouch. It's not just misaligned. It's been used misaligned until it beat the living tar out of itself.

Quote: "We wanted to see if we could rig it to work for the rest of the season..."

Nope. It's a dock extension until it's hauled. The coupling, the shaft, the cutless bearing, all are likely candidates for the junk pile. Maybe the engine mounts, too.

Even a small engine has a bunch of power to do harm. This one has been run when it must have been shaking everyone's teeth out, and kept running until it did serious damage to itself. There really is no quicky repair, because the joining points are damaged and cannot be held in alignment.

Sorry to be coming down with bad news.

[BreadandBoatses]

Originally Posted by Tetepare

Are the motor mounts shot?

One has bits starting to flake off but the others are fine from what I can tell.

Probably just replace them all to be safe.

[BreadandBoatses]

Originally Posted by Cheechako

That's tough. A lot going on there to completely understand.
-Do you know if it was ever in alignment? Many are not.
-When you say off 1/4", do you mean the faces are angled to each other or do you mean just off vertically but the faces are parallel?
-For any shaft to bore non fit/ovalizing you could use brass shim stock. NAPA auto parts in many thicknesses.
-Is the rear of the engine too high or too low to mate with the shaft coupling?
-DO you realize that adjusting the front engine mounts can raise or lower the rear alignment also? Often it's a matter of adjusting front and rear until you get there... and a PITA! ie: If you lower the front mount adjustment, the tail of the engine goes up by pivoting on the rear mounts.. etc.
Need a lot more info.....

Do not know history of alignment.
About 1/4” gap horizontal angle misalignment. There was a slight horizontal offset that I could fix and vertical angle can be fixed. It’s the horizontal angle that’s off because the slots on the feet bottom out before the engine is moved into the proper position.

[BreadandBoatses]

Also thank you all for the replies. I appreciate the help!

[Squanderbucks]

Shaft and coupler alignment is measured in thousands of an inch. Not inches. Even when it is way out of alignment but getting close you can not see even that by eye. Keys have to fit tightly in the shaft and sliding it into the coupler is almost a press fit. Depending on the type of coupler chosen.
The canary that was in this mine died long ago and nobody noticed he was at the bottom of the cage.
Experience and routine maintenance habits will hopefully alert the next time. Consume the large expense one the first “learning experiences”.

[SaltyMetals]

This may sound crazy, but i firmly bolt a shaft anode on the INSIDE of the prop shaft. That way if the shaft separates from the gearbox it is not going to drop out of the boat and then result in a sinking before you even know what happened.

Yes, twice in 20 years my shaft has separated from the gearbox so i take things cautiously.
Andrew

[Cadence]

Originally Posted by tkeithlu

Ouch. It's not just misaligned. It's been used misaligned until it beat the living tar out of itself.

Quote: "We wanted to see if we could rig it to work for the rest of the season..."

Nope. It's a dock extension until it's hauled. The coupling, the shaft, the cutless bearing, all are likely candidates for the junk pile. Maybe the engine mounts, too.

Even a small engine has a bunch of power to do harm. This one has been run when it must have been shaking everyone's teeth out, and kept running until it did serious damage to itself. There really is no quicky repair, because the joining points are damaged and cannot be held in alignment.

Sorry to be coming down with bad news.

A jury rig is an accident looking for a place to happen.

[crashley]

Strange that there isn’t enough adjustment to get it close. If the cutlass wears the shaft normally drops at the prop which means raising the engine
I would redrill to get it as close as possible and then drill and pin the shaft and coupling (selick pin)
And careful monitor it
And then redo when out of the water

[Pete7]

Originally Posted by Cadence

A jury rig is an accident looking for a place to happen.

Indeed, just as the owner is coming into an inlet in poor weather.

Lift the boat, replace the cutlass, engine mounts, coupling and stern gland. Say $600 if diy.

You might check the shaft to ensure its straight whilst its out and then polish it with progressively finer emery paper, until you have a dull shine like the back of baking foil.

Pete

[Searles]

Sounds like the whole shaft plu coupling plus engine mounts are shot ,probably due to long term lack of maintenance ,to try and cobble this lot to a slightly usable unit is a waste of time ,bottom line, fix it all properly ,it’s an accident waiting to happen .⛵️⚓️

[Midnight Son]

Originally Posted by Searles

Sounds like the whole shaft plu coupling plus engine mounts are shot ,probably due to long term lack of maintenance ,to try and cobble this lot to a slightly usable unit is a waste of time ,bottom line, fix it all properly ,it’s an accident waiting to happen .⛵️⚓️

Agree, trying to cobble it, might result in trashed stern tube/stuffing box/seal, if the attitude is, 'it held together so far, what could possibly go wrong on the next trip'?
Best wishes all.