How to get prop shaft coupling off .. Help!

A

Albert Ross

Well-Known Member
Joined
14 Oct 2004
Messages
230
Location
Troon and beyond
Visit site
I need to replace my boat's stern gland. Therefore, I need to get prop shaft out. I've split the coupling .. see picture
http://i233.photobucket.com/albums/ee277/B-FLAT34/118-1837_IMG.jpg
but I don't know how to get the aft half of the coupling off the shaft. I've removed the nut on the end of the shaft inside the coupling but can't get the coupling off . Any advice would be extremely welcome. Thanks
 
Not done that job myself, but looking at it as a mechanical task I would assume the flange is seated on spline or a keyed taper. Either way heat would be a touch risky so I'd go for some very technical clouts with a heavy hammer on the back of the flange. Better if you can get someone on the outboard end of the shaft with a nice heavy hammer or weight to oppose the force you'll be applying, assuming the prop hasn't been removed yet.

But, no claims.
 
Firstly have a very close look to see if the shaft is held by a pin or a woodruft key.
If a pin then this needs to be carefully drifted out.
Then get a nut just smaller than the diameter of the shaft and place between the the two flange faces ( in the centre). Replace the bolts joining the two flanges and tighten the bolts up evenly. As the bolts tighten up the temporary nut you have inserted will start to force the shaft away from the flange.
Good luck.
PS Don't use a hammer, you will cause damage.
 
It looks like a Volvo Penta coupling with a tapered locking pin and keyway - see here for a diagram. Guess you'd need to get the tapered locking pin out first, then use a puller.
 
That's a better answer than mine.


However, looking at the size of that flange, and having maintained a fleet of HGVs when we had a garage, I can't imagine distorting that with a 2lb hammer. I suppose it's to do with knowing how to hit.
 
Re: How to get prop shaft coupling off .. Help!

To get mine off (Petter), lots off heat and lots of whacks with a lump hammer, the puller we used jammed the flange by pulling slightly off centre, the hammer did it though.
 
Would support this method. No need for puller or hammer. Once the tapered pin is out the shaft only needs to move a small to pop out. If the end of the shaft is inset in the coupling, you may need to use a socket as a spacer rather than a nut.
 
Thank you .. yes I think it is a volvo penta coupling but I cant see a tapered pin .. .. I've tried hitting it quite hard with a hammer and I've tried forcing the shaft out by tightening the coupling back down with a nut inside as recommended above .. do I need to get a puller? if so, what and where ?
 
Can't help you with the coupling, but if you have a 2000 series Volvo engine, it would be a good idea to check the splines on your gearbox input shaft for excessive wear - described here

This is a common problem and my 2002 splines were worn out when I checked:

shaft-1.jpg
 
Obviously using a puller is the preferred method but looking at the photos I do not see enough space for an adequate puller.

If you are absolutely certain that there is no retaining pin then force, plus heat, is the only answer. As previously stated a spacer of some type will enable force to be applied by retightening the flange nuts and bolts and when tight a sharp blow should free the spline or taper. If all else fails you will possibly need to split and destroy the flange and fit a new one on reassembly otherwise its a gearbox out job! I cannot imagine that you would lightly want to undertake such a task!
 
Sometimes it can be very hard to see the pin holding the flange to the shaft. If you have tried using a spare nut ( or old socket) and it won't move then double check to see if there is a pin you have missed.
The other thing to double check is that there is not a nut on the end of the shaft ( hard to see sometimes, but use a small mirror of feel with your finger tip for the nut shape).
The advantage of the nut/socket method is that you are providing an even pressure and the most damage you are likely to do is shear the bolts, much better than spoiling the shaft or flange.
 
Thank you. Yes, I've used a mirror and found and removed the nut on the forward end of the prop shaft .. I haven't managed to find a tapered pin but will have another very close look . if I find a pin . how do I get it out ?!
 
If the shaft was held by a nut in the flange then on all the ones I have seen it will not have a pin but use a keyway. What you can do ( if you think you might shear the flange bolts) is get spare nuts and bolts and tighten them down ( with the nut/socket in place) untill either the bolts start shearing or the shaft starts moving. This way you run very little risk of damaging something important.
 
Thank you. This sounds right. Do I need to knock the key out of the keyway or will this slide out given enough pressure tightening the bolts against the socket /nut ? There are signs of a slot for a key on the aft end of the coupling.

She's a 10 year old boat . how tight will the corrosion between the shaft and the coupling hold?
 
Re: How to get prop shaft coupling off .. Help!

Once you have a puller or substitute trying to push the shaft out of the hub it could be useful to tap the hub with a hammer hoping the shock will break the bond. I have not done this but have read this suggestion in one of the boating comics.
 
You don't need to worry about the keyway. It will not stop the flange seperating from the shaft. Once the shaft seperates the key will pop out. Don't worry about shearing the bolts just give it a good go.
 
If it is a nut, then the flange is on a keyed taper. Use the spacer method, tighten up the coupling bolts and the flange will pop off. As it is on a taper it needs to only move a small amount. A tap with a hammer when the bolts are up tight might help, but if you get it as tight as you can and leave it overnight chances are it will be free in the morning.
 
You must log in or register to reply here.

Share this page

Top