Remove Prop shaft from Hurth HBW 150 transmission

[KDH]

I usually do the engine work on our Perkins 4.108 which is mounted with the belts aft and the transmission forward in the engine compartment. The prop shaft goes under the engine and into the Hurth transmission at an angle. It appears to be secured with two keys and a very large hex nut and pin which protrudes from the coupling. The problem is that neither myself nor my husband can break this nut loose without the shaft turning. I've never done this before and the last propeller shaft my husband removed was on a twin otter aircraft over 40 years ago. We need to remove the shaft from the coupling and back it out far enough to change the bellows on the PSS shaft seal while we are on the hard. Can't find any videos on you tube showing this configuration, have checked the Nigel Calder book and no luck. Is there a trick to this I'm missing? Have spent hours reviewing the forum threads as well. Any tips or hints greatly appreciated as I don't want to hire a mechanic to do what should be relatively simple. Currently in Ireland and this job is the only thing keeping us in the yard! Many thanks, Kim

[MARINE ENGINNER]

Originally Posted by KDH

I usually do the engine work on our Perkins 4.108 which is mounted with the belts aft and the transmission forward in the engine compartment. The prop shaft goes under the engine and into the Hurth transmission at an angle. It appears to be secured with two keys and a very large hex nut and pin which protrudes from the coupling. The problem is that neither myself nor my husband can break this nut loose without the shaft turning. I've never done this before and the last propeller shaft my husband removed was on a twin otter aircraft over 40 years ago. We need to remove the shaft from the coupling and back it out far enough to change the bellows on the PSS shaft seal while we are on the hard. Can't find any videos on you tube showing this configuration, have checked the Nigel Calder book and no luck. Is there a trick to this I'm missing? Have spent hours reviewing the forum threads as well. Any tips or hints greatly appreciated as I don't want to hire a mechanic to do what should be relatively simple. Currently in Ireland and this job is the only thing keeping us in the yard! Many thanks, Kim

photos please :-)


M.E

[KDH]

The connection here is too slow to post pics I'm afraid. I couldn't even get a fast enough connection to edit my location.

[Target9000]

I'm only speaking from my own experience with our coupling, but the flange that mounted on the transmission side had a nut that is secured with a bolt that screws into the side of the coupler. You remove this bolt to unlock the nut. The nut must then be unscrewed off the shaft to release the coupler which can then be slid off of the shaft. To break the nut we held the shaft in place from the back of the boat at the prop.

[sailr69]

I have done this and you need to do a few things, got a strap wrench? hold the coupling with the strap wrench and loosen the nuts by holding the spanner towards the center of the shaft instead of from the outside, like removing wheel lugs on a car. your bigger problem will be removing the coupling flange from the shaft. most likely it is frozen on the shaft. if so; you will need a die grinder to cut thru the coupling. after you remove the bolts pull the coupling apart and turn until the keyway is on top and then cut through the coupling into keyway to not harm the shaft. when installing the new flange, be sure to drill a dimple into the shaft before installing the new flange set screw. take your time and don't force anything keep it lubricated. do not use flame heat, might ruin the transmission seal. I am assuming you have a V drive. if this is the case, you may also have to raise the engine to get access to the log. having reread your post, sounds like to removed the bolts already connecting the flange to the trans.. your current problem is; removing the two set screws. line up the flange again and reinstall a couple bolts in the flange and then try to loosen the setscrews. loosen the lock nut first. some light tapping may help

[Maine Sail]

Does it look like this..



If so that is a double taper shaft, meaning taper at prop and at coupling..



If so it will usually require a large impact driver and a prop/hub puller. Even after you get the nut off a double taper the real fight has only just begun...

[bornyesterday]

Maybe some bright spark might have ground flats on the shaft for an open ended spanner?
Big Stillson wrench(es) can be used to grip a shaft but will mark it.
If the prop is still on you could thoroughly rope it to cleats and winches port & starboard on deck with rags to protect the hull from rope burns. If the P-bracket's strong enough you could use that.
Presumably if the propshaft is rotating freely it should be easy enough to avoid damaging the transmission?
A three-jaw puller and a tap with a mallet while it's tensioned will usually break the taper.
I'm sure you'll have checked the handedness of the nut so I won't even mention it.
There are probably better ways to do this but I can't think of any yet.

later edit: slotted shafts so we could use morse taper type drift keys would be nice.

[captainjay]

This is a V Drive Transmission from the description that is given.



Something like this.


The shaft goes thru the transmission and the coupler is on the back of the transmission facing forward sometimes they have a drive saver on them as well. The coupler and drive saver if equipped will have to be removed. If it's like this one you will need to remove the set screws and the bolts. A puller can be used or if you have a new coupler and angle grinder can be used to cut it and break it off. If it has a large nut on the end of the shaft that will have to be removed as well.

Jay

[model 10]

[QUOTE=KDH;1538407] I've never done this before and the last propeller shaft my husband removed was on a twin otter aircraft over 40 years ago.

If your husband could have ever removed the gearbox, dismantled it and then remove the prop drive shaft from a PT6 Turbo Prop engine, he is way over qualified to fix your boat, so no worries.

[KDH]

Originally Posted by captainjay

This is a V Drive Transmission from the description that is given.



Something like this.


The shaft goes thru the transmission and the coupler is on the back of the transmission facing forward sometimes they have a drive saver on them as well. The coupler and drive saver if equipped will have to be removed. If it's like this one you will need to remove the set screws and the bolts. A puller can be used or if you have a new coupler and angle grinder can be used to cut it and break it off. If it has a large nut on the end of the shaft that will have to be removed as well.

Jay

Thanks Jay for posting the pics and the info. This is the set up we have only it's blue because the engine is a Perkins and not nearly as clean and rust free! Unfortunately, I don't have a new coupler nor an angle grinder at the moment. I will ask around the yard and see if I can borrow a puller.

[KDH]

[QUOTE=Guy;1538544]

Originally Posted by KDH

I've never done this before and the last propeller shaft my husband removed was on a twin otter aircraft over 40 years ago.

If your husband could have ever removed the gearbox, dismantled it and then remove the prop drive shaft from a PT6 Turbo Prop engine, he is way over qualified to fix your boat, so no worries.

Guy, questioning the tale's of one's spouse do not lead to a long marriage and we've been married over 25 years! He was an aircraft tech before he became a pilot. Unfortunately pilot's don't fix things they tell other people (that would be me) to fix them. Seriously, I am the boat's mechanic.

[KDH]

Originally Posted by Maine Sail

Does it look like this..



If so that is a double taper shaft, meaning taper at prop and at coupling..



If so it will usually require a large impact driver and a prop/hub puller. Even after you get the nut off a double taper the real fight has only just begun...

Thanks also for the pics. I do know it is tapered at the prop end and I do not want to have to take the prop apart to take it off. I also don't want to wrap a rope around it if at all possible as it's a Max-prop. It does look more or less like your pictures.

[KDH]

Maybe I should have also asked if I remove the prop shaft from the coupling do I also need to replace the cutlass bearing? I just paid someone to do that two years ago. The prop is a max-prop, the old style with 23 or so parts. The installation video at PYI makes it seem like this is an easy job. I guess if it is that difficult I may as well splash out on flexible shaft saver as well (if I can find one). Many thanks to everyone who has chimed in.

[tdoster]

In my case. It FAR was easier to remove the prop and pull the shaft and coupling into the boat complete. Then slide the PSS and bellows over, etc. So, just have to remove the 4 bolts for the coupling and pull the shaft in a few inches to clear the current packing.

[tdoster]

Originally Posted by KDH

Maybe I should have also asked if I remove the prop shaft from the coupling do I also need to replace the cutlass bearing? I just paid someone to do that two years ago. The prop is a max-prop, the old style with 23 or so parts. The installation video at PYI makes it seem like this is an easy job. I guess if it is that difficult I may as well splash out on flexible shaft saver as well (if I can find one). Many thanks to everyone who has chimed in.

You should not have to replace the cutlass if it is only 2 years old unless the alignment is really bad. It is an easy job in most cases (PSS Installation), but with a V-Drive, you have to think backwards where many cases it is easier to pull the shaft into the boat for cutlass and packing work than it is to pull it out- a normal drive would be impossible to pull in, so most people don't think the other way.

You may not have room for a flex, so measure carefully. And in my mind, they just compensate for bad alignment or really worn motor mounts.