# Shaft coupling removal and reinstallation



## downeast450 (Jan 16, 2008)

After reading stories of the difficulties removing a shaft coupling I started spraying the one on our Atomic 4 with PBB a year ago. Yesterday I began tightening the three extra long bolts that are shimmed with washers and pull the shaft back to the transmission flange. There is a socket in the center of the coupling that is pushing back on the end of the shaft, forcing it out of the coupling as I tighten the bolts. Thank you Mr. Calder. It is working. The coupling has moved about 3/4" off the shaft. I did apply some heat on two occasions. Because of the limited space between the flange on the engine / transmission side and the transmission housing, washers have to be added as the socket pushes the shaft further out of the coupling flange. There isn't a lot of working room. It is a one hand operation, lying on my side fighting off muscle cramps! Fun! I started with two washers on each bolt and have added two more. I am out of 3/8" lock washers so I had to stop. I expected it to "let go" before the shaft traveled 1/2"? It is well passed that! I will find out next week how many washers it takes. Anybody care to guess?

What is now beginning to concern me is how I will get it back on to the depth it was when I began. I haven't read any advice about this. I will certainly "polish" both the shaft and the inside of the coupling but don't have a plan for "hammering it home"? Is putting one of these things back on a problem, too? I suppose I can heat the flange and cool the shaft?



















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## captbillc (Jul 31, 2008)

after you install a new seal you would not want to ruin it with a hot flange ( if this is the flange you are talking about ) i have used a special puller that fits in the hole on the flange and screws on the shaft threads. use a little lubrication so the flange & shaft don't seize together.


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## downeast450 (Jan 16, 2008)

Different flange, Capt.

Down


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## gtod25 (Aug 5, 2000)

*By hand....*

The coupling should go on by hand. Take the shaft and the flange to a machine shop and have them check the shaft for alignment and fit the flange. The flange should slide on/off the shaft with minimum effort. Make sure they drill a "dent" for the locking bolt, and that the bolt has a retaining wire hole to permit it to be lock wired in place.

Ref PBB, great stuff but use caution around gaskets etc;

PB Penetrating Catalyst FAQ's

Have fun.


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## erps (Aug 2, 2006)

> I started with two washers on each bolt and have added two more. I am out of 3/8" lock washers so I had to stop. I expected it to "let go" before the shaft traveled 1/2"? It is well passed that! I will find out next week how many washers it takes. Anybody care to guess?


I can still see shaft through the lock bolt hole, so count on another inch of travel at least. I'd buy a couple sets of shorter bolts.



> What is now beginning to concern me is how I will get it back on to the depth it was when I began. I haven't read any advice about this.


Take a file and make a light mark on the shaft where the flange ended before you clean it up with fine sandpaper.


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## Maine Sail (Jan 6, 2003)

downeast450 said:


> After reading stories of the difficulties removing a shaft coupling I started spraying the one on our Atomic 4 with PBB a year ago. Yesterday I began tightening the three extra long bolts that are shimmed with washers and pull the shaft back to the transmission flange. There is a socket in the center of the coupling that is pushing back on the end of the shaft, forcing it out of the coupling as I tighten the bolts. Thank you Mr. Calder. It is working. The coupling has moved about 3/4" off the shaft. I did apply some heat on two occasions. Because of the limited space between the flange on the engine / transmission side and the transmission housing, washers have to be added as the socket pushes the shaft further out of the coupling flange. There isn't a lot of working room. It is a one hand operation, lying on my side fighting off muscle cramps! Fun! I started with two washers on each bolt and have added two more. I am out of 3/8" lock washers so I had to stop. I expected it to "let go" before the shaft traveled 1/2"? It is well passed that! I will find out next week how many washers it takes. Anybody care to guess?
> 
> What is now beginning to concern me is how I will get it back on to the depth it was when I began. I haven't read any advice about this. I will certainly "polish" both the shaft and the inside of the coupling but don't have a plan for "hammering it home"? Is putting one of these things back on a problem, too? I suppose I can heat the flange and cool the shaft?
> 
> ...


Down,

This is supposed to be a light press fit. If you "polish" the OD of the shaft and ID of the coupling you will very likely lose this very delicate fit tolerance. It is not a bearing press fit like a cutlass to a strut but it is supposed to be a light press fit. If it just slides back on this = BAD!

As for getting a new coupling back on you can heat the coupling and cool the shaft or just guide it into place and use a wood mallet to "tap" the shaft into the coupling (usually takes 2 people to get it started). I color the dimple (spotting) in the shaft with a red sharpie marker then peer through the set screw hole with a flash light until it is lined up perfectly. If I am alone it takes MANY trips up and down the ladder to get it just perfect. The red dot makes it easier to see the spotting in the shaft.. I suspect someone on the island can fit and face a new coupling for you if your fit is destroyed...

P.S. Get full length threaded bolts and this will go faster.... You can also use threaded rod if you can find it in the right thread...


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## downeast450 (Jan 16, 2008)

Thank you all for the information. I could put a longer socket in the space and probably will. The reason I was thinking about just adding washers is because of how tricky it is to get the socket to remain aligned with the end of the shaft and not fall out of the gap as you bring the flange up close enough to hold it while you get a bolt started. With one hand!

Maine, I will not "polish" it. Thanks! Heat is wonderful! Not sure how I could strike a couple of blows with a mallet. Perhaps a levered piece of 2x4 that pushes on the flange when I tap near the end?

Down


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## CalebD (Jan 11, 2008)

Down,
Went through this with our A4 a couple of months ago. Pressing the coupling and shaft apart was torturous given our engine compartment. We found our bronze shaft to be worn at the stuffing box so we cut the shaft in 2 and it was much easier to remove the flange on a shop work bench. 
2011, November 30th. Begin drive train rebuild | Odalisque
You probably have another 3/4" to 1" to go pressing your shaft out.

If your shaft is bronze you should consider that it might be easier to cut the shaft and pay around $200 for a new SS shaft. Have a prop shop spin your prop for balance and they can 'fit and face' your old coupler and make re-installation a very easy job by comparison to what you are doing now - which is a form of torture.
If your shaft is bronze it is likely 20 - 40 years old, therefore worth replacing.
You are planning on replacing the Cutless bearing as well as the shaft log hose, right?
Clean up and re-pack stuffing box and you have an as new drive train.

Good luck.


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## gtod25 (Aug 5, 2000)

*Listen to the master, O great one, MS.....*

I stand corrected. Sorry MS, If I knew you were on I wouldn't even have posted. I must have missed the "press fit" part of your excellent instructional blog. Thanks for the correction.

Gerry


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## downeast450 (Jan 16, 2008)

CalebD,

That is my plan. It is a tedious PITA working in that cramped space. My shaft is ss. It is moving slowly, one washer at a time, Ha! I have plenty of time to finish forcing it out of the flange this way. It has become one of the tasks that I spend an hour or two on and then leave it until the next day I am aboard. If it wasn't moving I would be concerned. I think I will change the socket for a deeper one. With the shaft already moved 3/4" it may be easier to get a socket to stay put while I bring up the bolts.

PBB is great stuff but should be used carefully. I use paper towels for masking when I spray that stuff and remove the contaminated paper immediately. It is coming out of the flange with "color" so it is helping. WD-40 might be a better lubricant now that things are moving.

Taking care of the shaft is the last big chore left that came with the boat.

Down


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## Maine Sail (Jan 6, 2003)

gtod25 said:


> The coupling should go on by hand. Take the shaft and the flange to a machine shop and have them check the shaft for alignment and fit the flange. *The flange should slide on/off the shaft with minimum effort.* Make sure they drill a "dent" for the locking bolt, and that the bolt has a retaining wire hole to permit it to be lock wired in place.
> 
> Ref PBB, great stuff but use caution around gaskets etc;
> 
> ...


The fit of a straight coupling to a shaft is supposed to be a an interference fit NOT a clearance fit. With an interference fit the coupling DOES NOT and SHOULD NOT just slide on because the shaft is ever so slightly bigger than the coupling. Good shafting shops, that know what they are doing, will fit them as a light interference fit.

Western Branch Metals, the largest supplier of prop shafting in the country, suggests that the shaft OD should be about .0003" - .0005" larger than the ID of the straight coupling. This will require a light tapping or heating to make it fit into place.

If you purchased couplings that fit like that, just slid on, they were incorrectly fit to the shaft. This can lead to shaft fracturing or the shaft backing out of the boat altogether.


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## CalebD (Jan 11, 2008)

downeast450 said:


> CalebD,
> 
> That is my plan. It is a tedious PITA working in that cramped space. My shaft is ss. It is moving slowly, one washer at a time, Ha! I have plenty of time to finish forcing it out of the flange this way. It has become one of the tasks that I spend an hour or two on and then leave it until the next day I am aboard. If it wasn't moving I would be concerned. I think I will change the socket for a deeper one. With the shaft already moved 3/4" it may be easier to get a socket to stay put while I bring up the bolts.
> 
> ...


Down,
You are a man with a lot of patience and determination. It really was torture trying to do this in the engine compartment of our Tartan 27'. I sure hope your Islander 28' has better access then we had.
If you must persist (and it sounds as though you must) keep applying the pressure evenly and methodically. There is a small chance you could deform the shaft coupling or output coupling if the pressure is uneven. There is a very long thread on the Moyer forums that details how a fellow Afourian had to replace his output shaft and get a new coupling after pressing the shaft out: Indigo - Moyer Marine Atomic 4 Community - Home of the Afourians
Good luck. Patience and persistence.


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## SloopJonB (Jun 6, 2011)

downeast450 said:


> I expected it to "let go" before the shaft traveled 1/2"? It is well passed that! I will find out next week how many washers it takes. Anybody care to guess?


The shaft should be buried nearly the entire length of the coupling, not just a little way in - get a deep socket or a bunch of thick washers and keep going.

Lock washers are not needed, they just add a little flex to the process as you flatten them out.


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## itsaboat (Sep 28, 2011)

downeast450 said:


> Maine, I will not "polish" it. Thanks! Heat is wonderful! Not sure how I could strike a couple of blows with a mallet. Perhaps a levered piece of 2x4 that pushes on the flange when I tap near the end?


Down, I think RC was referring to tapping the end of the propeller shaft from the outside to fit the flange back into place? Thus the many trips down the ladder he was referring to if I am not mistaken.

I am getting ready to do this exact thing to replace a stuffing box tube with a PSS dripless as soon as I can get the marina to finish the bottom job on the damn Hunter that is occupying the only available trailer. 

After reading this, I am debating whether to pack a gear puller, PBB, some lag bolts and a big can of washers, or carry a hacksaw up the ladder and just be done with it.

Good luck!


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## downeast450 (Jan 16, 2008)

JonB,

The reason for the lock washers is their outside diameter. They are small enough to fit on the bolt where the clearance to the coupling is quite limited. A regular flat washer has too large an OD.

Down


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## downeast450 (Jan 16, 2008)

Eric,

That makes sense! I would be concerned about the force being transmitted along the shaft to the transmission. I could fit a 1/2" steel plate between the transmission flange and the shaft flange. That would stand some whaling and pounding. Perhaps tapping? Up and down the ladder takes the place of the Stair Climber. There are so many rewards from working on small boats.

Down


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## Brent Swain (Jan 16, 2012)

Boil your coupling in a pan of water, and pack ice around the shaft for a half hour, before putting them together. That should make it easy. If you have heated it in place , you may have warped the shaft. Check that out before re-installing them. Put the coupling on the shaft and resurface the coupling in a lathe. Cutting the shaft key way can also warp it out of alignment.


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## sailne1 (Feb 6, 2003)

I would recommend replacing the coupling.......Last summer I removed my Universal Diesel/Trans/coupling/shaft. My yard advised that the original tolerance cannot be maintained with an old coupling. The thin film of rust that was removed by the PBB will not allow for a snug fit once the parts are cleaned. My coupling would just slide onto the shaft with no force whatsoever. Check out Boat Propellers, Inboard Propellers, Cutlass Bearings, Zinc Anodes, Prop Shafts, Shaft Seals, and more I purchased a new coupling for my 3/4 shaft for $50-60. Installed a new packing gland while I had everything apart....... also from DBYS. The fun part is going to be aligning the flanges to a .002 tolerance....Have patience and a good set of feeler gauges. Be sure to recheck the flange alignment after 10hrs of operation.

Fair Winds,


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## sfchallenger (May 17, 2011)

I would agree with dry ice for the shaft and boiling water for the coupling. What about some bar or 'c' clamps (gently) applied rather than a hammer? I would be carefull not to overdo it, but I'd think you might have better luck with even pressure distributed around the coupling.

Best,
h


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## downeast450 (Jan 16, 2008)

You have to love this forum!

Let me see? 

It is easy to imagine that a couple of ten thousands of black iron has washed out of the coupling as I slowly force it off with the help of PBB. I hadn't considered replacing it before I began. I confess ignorance of the type of fit involved. I expected it to "let go" because I was thinking of a tapered fit not a straight one.

I don't think the heat I applied to the outside of the coupling using a very low flame on a simple propane torch would have been enough to warp anything? I will check it.

Using temperature differences to expand the coupling and shrink the shaft will be my approach for installation.

This is a Moyer rebuilt I installed three years ago. I bolted the flange that came on the "new" A-4 up to the "old" shaft flange and used a "trick" suggested by one of my Downeast friends. Three cleaan, dry pieces of notebook paper were my feeler gauges. If all three are trapped by the flange, one at each bolt hole, as you rotate the shaft, "She will be close enough Deah!" It did work. No vibrations.

Great information! Thanks all.

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## pschoonveld (Sep 9, 2005)

I did this same project with my Tartan 34 over Christmas.

I recommend cutting the coupling. I used a 4" angle grinder and a Bosch oscillating tool to cut through the coupling on top of the keyway and then 180 degrees on the other side. It was messy, but way better than messing with heat and cold approaches for the reasons you noted. I also didn't put a scratch on the shaft. Had it not been for the scoring I found at the stuffing box, I would have easily been able to reuse the shaft. The whole thing took 45 min, tops.

Next, check the clearance between the dripless/stuffing box of your choice and the coupling. If you have an inch to spare, your next coupling could be a split coupling. The advantage is you don't press the shaft onto the coupling. Instead, the coupling has a slot that closes when you bolt it down. The downside is the coupling is about an inch longer.

Should you not have the space for a split coupling, make sure you have a small sledge to seat the shaft onto the coupling. I ended up using a scrap piece of 3" drive shaft to wail it into place. Every time you hit the shaft, the engine moves forward on the mounts and it takes forever. Not a fun project, but it's the only option unless you hoist the engine and slide the pressed coupling/shaft combo back through the packing and stern tube.

While you're in the neighborhood, have a look at your cutlass bearing and strut. A bearing is only $20 and the easiest time to replace it is when the shaft is out. If your strut needs rebedding, as mine did, it's a good time to get it taken care of. On many boats, mine included, the rudder is in the way of removing the shaft and dropping the strut was the only way to get the shaft out, short of hoisting the engine or dropping the rudder.

Finally, if you haven't had enough good advice from your friends yet, consider having a prop shop balance your prop. Mine had significant differences in pitch and diameter. Friends who've had it done say it made a huge difference in vibration and the cost for a 2 blade is only $200-ish.

Have fun...


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## Skipaway (Jun 2, 2008)

pschoonveld writes: 
>Next, check the clearance between the dripless/stuffing box of your choice and the coupling. If you have an inch to spare, your next coupling could be a split coupling. The advantage is you don't press the shaft onto the coupling. Instead, the coupling has a slot that closes when you bolt it down. The downside is the coupling is about an inch longer.

Downeast: a split coupling was recommended to me by prop shop that mostly works on fishing boats. Makes sense, except I wonder about balance. Other with experience or comments?

Also wondering what necessitated this work? (I have similar work coming up. the flange key sheared on mine, plus strut need re-bedding.)


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## Maine Sail (Jan 6, 2003)

Skipaway said:


> pschoonveld writes:
> >Next, check the clearance between the dripless/stuffing box of your choice and the coupling. If you have an inch to spare, your next coupling could be a split coupling. The advantage is you don't press the shaft onto the coupling. Instead, the coupling has a slot that closes when you bolt it down. The downside is the coupling is about an inch longer.
> 
> Downeast: a split coupling was recommended to me by prop shop that mostly works on fishing boats. Makes sense, except I wonder about balance. Other with experience or comments?
> ...


Split couplings do not need to be "longer". Buck Algonquin makes one for many engines that is actually shorter and I install a bunch of them. Still need a fit & face but easier install....

This one is for a 1" shaft and a Hurth HBW box..


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## downeast450 (Jan 16, 2008)

Charlie,

I am removing the shaft to replace an aging cutlass bearing before it causes any problems and to renew the stuffing box coupling hose. Both came with the boat. I don't plan to change to a dripless connection. 

Down


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## downeast450 (Jan 16, 2008)

This looks like a good solution to the new coupling from Moyer Marine.

(OREV_14.0_540) Direct drive prop shaft coupling, with split hub (3/4 inch)

The split hub design insures a tight fit between the coupling and prop shaft as well as facilitating removal of the coupling in the future.

Direct drive prop shaft coupling, with split hub (3/4 inch)
Price: $175.00

Any one used one of these?

Down


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## Brent Swain (Jan 16, 2012)

Don't rely on a grub screw with an indentation in the shaft to stop the shaft from pulling out of the coupling when reversing. I've seen them do that, and come close to sinking the boat, several times. I use a 5/16th bolt right thru the coupling and shaft. On split couplings, the bolts score the shaft by about half the diameter of the bolt.


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## SloopJonB (Jun 6, 2011)

Brent Swain said:


> Don't rely on a grub screw with an indentation in the shaft to stop the shaft from pulling out of the coupling when reversing. I've seen them do that, and come close to sinking the boat, several times. I use a 5/16th bolt right thru the coupling and shaft. On split couplings, the bolts score the shaft by about half the diameter of the bolt.


Another of God's cosmic jokes. If you WANT to remove your coupling, good luck - heat, large hammers, powerful cutters etc. will be required.

If, on the other hand, you DON'T want it to separate, merely putting it in reverse is very possibly all that will be required.

*Brent*, re: your reference to running a bolt all the way through - could you just drill & tap part way into the shaft or would that cause balance problems? Also, I don't understand your last sentence - "score the shaft...." Can you elaborate?


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## pschoonveld (Sep 9, 2005)

Maine Sail said:


> Split couplings do not need to be "longer". Buck Algonquin makes one for many engines that is actually shorter and I install a bunch of them. Still need a fit & face but easier install....


I really wish I had known about the split coupling with a shorter length. I can't stress enough how much easier this would have made the install.


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## Brent Swain (Jan 16, 2012)

The solid coupling is put on and the holes are drilled so half the hole is in the side of the shaft.


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## Skipaway (Jun 2, 2008)

downeast450 said:


> Charlie,
> 
> I am removing the shaft to replace an aging cutlass bearing before it causes any problems and to renew the stuffing box coupling hose. Both came with the boat. I don't plan to change to a dripless connection.
> 
> Down


I'm doing all that + more; also plan to stick with conventional stuffing. Interesting that you have a 3/4" shaft; mine is 1/2", so fewer options. I don't have much to offer, so I'll follow the thread so as not to hijack.


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## SloopJonB (Jun 6, 2011)

Brent Swain said:


> The solid coupling is put on and the holes are drilled so half the hole is in the side of the shaft.


Do you drill opposing holes or only on one side? Do you tap the holes in the shaft or just oversize them to the major diameter of the fastener so the shank of the fastener can simply slip into the hole - like a pin or a way oversized grub screw?


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