Can You Just Cut A Prop Shaft And Put In A Universal Joint?

[CaptainBob]

Go easy on me. Just a thought. Might not even be necessary. Probably stupid. Bit of a bodge. But...

I need to replace the hose section of my stern gland thing. As per other thread (requesting engineer recommendations) may get a professional to do it. I think it may be awkward to get the prop shaft out of the coupler, and possibly impossible to then pull the shaft aft far enough to get the existing stern gland off - so an engine lift might be required to do it. Which obviously would be best avoided.

Wondering if it's possible to simply cut a section out of the shaft, do what's needed, and then install a universal joint (et al) in the gap?

I guess I'd need to install some bearing for the shaft, aft of the joint, in-line with the cutlass bearing. Easier to just organise an engine lift?

Or?

 

[Tranona]

If the shaft won't move back far enough (fouling the rudder is the usual reason) then the alternatives are dropping the rudder (although if there is a cut out, removing the prop might help), or moving the engine forward on its beds. Don't think about cutting the shaft!

 

[Neil_Y]

No

Simple answer is no, as a UJ won't take thrust loads. With uj's you need two (cardan shaft) co planar but offset and a thrust bearing, you could use a Marine Joint, single cv that takes thrust, and you can add a forward bearing.

But do you really need to?

 

[CaptainBob]

Fixed skeg in the way, between prop and rudder. Engine doesn't have a lot of room to move and it's HUGE (6 litre, 6 cylinder Ford 2715E).

 

[ffiill]

Whilst cutting shaft is not best idea its quite easy to rejoin using a pair of clamp fitted half couplings.
These are same as any half coupling except that instead of being secured to shaft by key and locking grub screw the end of the coupling bored to shaft diameter engineering fit has two slots cut in it;a pair of wings either side of slots which are through bolted allowing the coupling to be tightened up onto shaft, Similar to way sections of car exhaust are fitted.Or you can get two standard half couplings bored and key wayed to size and the shaft fitted with new keyways.
Any propshaft specialist can do this-not just marine-and can supply the half couplings.
I once added about a half meter to a shaft using this system.

 

[alahol2]

Or just a rigid coupling ? or 2? But a 6 litre engine must produce a hell of a torque.

 

[Finbar]

Same problem on a Malo 36. Friend of mine was told by Malo to take an angle grinder and cut the shaft to get access to the shaft log to renew the cutless bearing. The advice was to then fit a new shaft.

Might not be as daft as it sounds if you cost the alternatives.

 

[clyst]

Same problem on a Malo 36. Friend of mine was told by Malo to take an angle grinder and cut the shaft to get access to the shaft log to renew the cutless bearing. The advice was to then fit a new shaft.

Might not be as daft as it sounds if you cost the alternatives.

Capt has said the shaft cant be removed aft due to skeg nor forward 'cos of engine therefore a new shaft cant be fitted . Or am I missing summin??

 

[CaptainBob]

Yeah I thought that Clyst - assumed I was missing something.

One of these looks good:

http://www.ruland.com/ps_couplings_rigid_mscc.asp

But I guess very difficult to machine a keyway into the existing shaft insitu?

 

[robmcg]

How much long is the shaft inside the boat and how much room do you have between the gearbox and stern gland. Just wondering if you could cut the shaft and install an aquadrive. You would have to do a bit of measuring though but you have up to about 25mm tolerance in most directions. Might give you the amout of room you need?

www.halyard.eu.com/Knowledge/prop_shaft_vibration.html

 

[fisherman]

It may be possible to remove the gearbox: I have done this in situ on a 6 cyl ford with PRM box.
Then you have enough room to slide the gland off the shaft. To remove the shaft coupling use the coupling as a puller, put a spacer (eg socket) on the shaft end and wind the coupling halves together, having made sure all grub screws etc. are out.

 

[oldharry]

Same problem on a Malo 36. Friend of mine was told by Malo to take an angle grinder and cut the shaft to get access to the shaft log to renew the cutless bearing. The advice was to then fit a new shaft.

Might not be as daft as it sounds if you cost the alternatives.

So how does he get the new shaft in without lifting the engine? If lifting the engine anyway, why destroy the old shaft?

 

[Heckler]

Go easy on me. Just a thought. Might not even be necessary. Probably stupid. Bit of a bodge. But...

I need to replace the hose section of my stern gland thing. As per other thread (requesting engineer recommendations) may get a professional to do it. I think it may be awkward to get the prop shaft out of the coupler, and possibly impossible to then pull the shaft aft far enough to get the existing stern gland off - so an engine lift might be required to do it. Which obviously would be best avoided.

Wondering if it's possible to simply cut a section out of the shaft, do what's needed, and then install a universal joint (et al) in the gap?

I guess I'd need to install some bearing for the shaft, aft of the joint, in-line with the cutlass bearing. Easier to just organise an engine lift?

Or?

Many years ago I did this using Rover 2000 UJs. I used 2 sets, back to back, to get the necessary articulation.
Stu

 

[Finbar]

On the Malo I am told you can't withdraw the shaft with the cutless bearing in place as it hits the rudder/skeg on the way out. Hence the need to cut and discard. However you can put a new one back in when the cutless bearing is removed - there is sufficent play to allow this. You then slide the new cutless bearing up the new shaft and press into place,

Haven't done it myself (yet) but sounds feasible. Could be worth a look, as it is probably the cheapest option if it works.

 

[rosssavage]

So if you can install with the cutlass removed, why not unbolt the cutlass, slide it up the shaft to clear its mounting and pull the shaft?

 

[Tranona]

You are assuming of course that you have to actually move the shaft. If you (or your mechanic) is just replacing the packing there will be no need. Even replacing the cutless if it is on an external screwed housing could be achieved without disturbing the shaft.

However if the stuffing box is on a rubber hose you will have to disconnect the shaft and remove the coupling. You may well find that removing the prop will allow the shaft to slide back enough to do this. Your mechanic will suss out what is possible once he sees it.

 

[clyst]

Many years ago I did this using Rover 2000 UJs. I used 2 sets, back to back, to get the necessary articulation.
Stu

Articulation yes but UJs are not built to take thrust . Unless of course a thrust block is incorperated .

 

[Finbar]

I am not sure why the cutless cannot be slid down the shaft on the Malo and removed that way - probably a clearance issue, or perhaps it needs to be driven out of the shaft log from inside. I do know that it cost my friend about €1200 and a great deal of trouble to have a new bearing installed due to reluctance to cut the shaft.

Presumably if you could get it started out, you could cut off the bit outside the shaft log and continue to ease out.

Given the cost of engineers time, about £40 to £50 an hour in the UK, might be better to bite the bullet. A new shaft would probably be equivalent to 4 or 5 hours time, not to speak of lifting, cradle and storage charges.

 

[SHUG]

In my limited experience, once you detach the inboard end of the shaft and if you can remove the cutless bearing there may be enough flexibility to get the shaft past the skeg. I suppose it depends exactly on the lengths inboard and outboard. Good luck!!

 

[DownWest]

Articulation yes but UJs are not built to take thrust . Unless of course a thrust block is incorperated .

I can think of several cars that used Hardey Spicer joints in end thrust situations as suspension members. Jags and Triumphs are two. CV joints, of course, not. With the very slight angular variation in a prop shaft, simple Hook's joints (Like HSs) would be fine.