Prop shaft advice please.

[ROBDEN]

Hi.

 

A couple of days ago I lost all drive on the boat.

When I looked, I could see that the prop shaft had slid out of the split half coupling.

Checking the bolts I found that two of them were loose.

I bought four new bolts and replaced them and all is ok now.

 

What I noticed though, was, to get the shaft back inside the coupling I had to push down on the shaft probably by about 2-3 mm maybe even 4 mm.

 

Is it worthwhile raising the rear of the engine by that amount or leave well enough alone?

 

Vetus engine, technodrive box, R+D flexible coupling, split half coupling, Vetus stern gland.

 

Any advice will be much appreciated.

 

Rob….

[Guest]

Hi.

 

A couple of days ago I lost all drive on the boat.

When I looked, I could see that the prop shaft had slid out of the split half coupling.

Checking the bolts I found that two of them were loose.

I bought four new bolts and replaced them and all is ok now.

 

What I noticed though, was, to get the shaft back inside the coupling I had to push down on the shaft probably by about 2-3 mm maybe even 4 mm.

 

Is it worthwhile raising the rear of the engine by that amount or leave well enough alone?

 

Vetus engine, technodrive box, R+D flexible coupling, split half coupling, Vetus stern gland.

 

Any advice will be much appreciated.

 

Rob….

If you had to push the coupling downwards, sounds like the engine has gone out of alignment, likely the engine mounts have settled. Did you fit new locknuts on the half coupling?

Doubt if just raising the rear mounts will keep the alignment correct. I made a crude but effective clamp to stop the shaft from wobbling around whilst setting the alignment. Feel free to pm me if you need more info.

ps often a vetus stern gland will drip if there is serious misalignment.

Edited April 11, 2015 by Guest

[ROBDEN]

If you had to push the coupling downwards, sounds like the engine has gone out of alignment, likely the engine mounts have settled. Did you fit new locknuts on the half coupling?

Doubt if just raising the rear mounts will keep the alignment correct. I made a crude but effective clamp to stop the shaft from wobbling around whilst setting the alignment. Feel free to pm me if you need more info.

ps often a vetus stern gland will drip if there is serious misalignment.

Thanks Cat'.

Should have said new bolts AND nuts.

Sending pm.

 

Rob....

[MtB]

I'd suggest raising the rear engine mounts to align properly.

 

Exact alignment isn't critical with rubber engine mounts and flexible coupling but no harm in reducing the propshaft stress by lining them up properly in the first place. There is a school of thought that this misalignment might have caused the shaft to work itself out of the coupling in the first place. I'd be keen to align correctly were it my boat.

 

 

MtB

[Guest]

I'd suggest raising the rear engine mounts to align properly.

 

Exact alignment isn't critical with rubber engine mounts and flexible coupling but no harm in reducing the propshaft stress by lining them up properly in the first place. There is a school of thought that this misalignment might have caused the shaft to work itself out of the coupling in the first place. I'd be keen to align correctly were it my boat.

 

 

MtB

I wondered about that. I have heard of a few split couplings coming loose.

[bizzard]

Thanks Cat'.

Should have said new bolts AND nuts.

Sending pm.

 

Rob....

It would be better than nothing to raise the engine up a bit. I'd do all four mounts equally. If you have the usual rubber mounts hold the studs tops still with a spanner whilst slackening off the top self locking nuts. Then, screw up all four nuts underneath the mounting feet equally in half turn increments until the half coupling slips on and off smoothly, and then tighten down the top self locking nuts. As I said, better than doing nothing although it should be aligned properly taking all angles into account..

Those slide on clamp type half couplings often have a location pinch bolt for extra security located on one side of the sliding part. This has a pointed ended bolt which screws into an indent in the shaft.

[Timleech]

If it's the common white R&D coupling which sits between the two flanges, they are not a fully flexible coupling and do need the alignment to be pretty good, get the engine properly aligned to reduce wear on the prop shaft and reduce the chances of future trouble. The Vetus sterngear does have a bit of flexibility as well, but best to get it right.

 

Tim

[Guest]

If it's the common white R&D coupling which sits between the two flanges, they are not a fully flexible coupling and do need the alignment to be pretty good, get the engine properly aligned to reduce wear on the prop shaft and reduce the chances of future trouble. The Vetus sterngear does have a bit of flexibility as well, but best to get it right.

 

Tim

Agree 100%. It knocks hell out of the propshaft seals/inner bearing if the alignment goes a long way out.

Another point th e vetus mounting nuts (16mm IIRC) have a habit of shaking loosen vibrate down the threads and I'll take a punt that is what has happened here! I rplaced the top ones with nylocks, and frequently chec the lower nuts tightening them UPWARDS. A tap with a small hammer confirms they are tight/loose.

[Paul C]

If its an R&D semi-flexible style coupling, then one of the bolts will (should) be red and this can be used for the angular alignment of the engine, using feeler gauges. If you simply raised the rear 4mm then you'll undoubtedly put the angular alignment out (unless its that far out already, that it reduced it...) Basically, its worth aligning the engine in all 4 axes (horizontal position, vertical position, horizontal angle, vertical angle). The better its aligned, the less wear on components so its worth doing right.

[ROBDEN]

Thanks all.

 

If the weather is ok tomorrow I'll do it then.

 

Rob....

[ROBDEN]

A bit earlier I thought I would get the correct size spanners ready, to adjust the engine mounts tomorrow.

When I put the spanner on the locking(?) nut at the bottom of the mount, I realised that there was no washer there...I thought.

Wrong. There was a washer there. I just couldn't see it as it had sunk into the mount.

 

That's what has caused the mis-alignment, the engine mount has collapsed.

So, off to the shop tomorrow or Monday to spend some more money.

 

I hate boats.

 

Rob....

[Guest]

A bit earlier I thought I would get the correct size spanners ready, to adjust the engine mounts tomorrow.

When I put the spanner on the locking(?) nut at the bottom of the mount, I realised that there was no washer there...I thought.

Wrong. There was a washer there. I just couldn't see it as it had sunk into the mount.

 

That's what has caused the mis-alignment, the engine mount has collapsed.

So, off to the shop tomorrow or Monday to spend some more money.

 

I hate boats.

 

Rob....

At least you know what it is now! Hope it is easy to fix for you.

[ROBDEN]

At least you know what it is now! Hope it is easy to fix for you.

 

Thanks.

 

Trad stern, deep narrow engine 'ole. Nothing easy on this boat apart from emptying pockets.

 

As I said. I hate boats.

 

Rob....

[Chick-Chick-Chicken]

It is not recommended that a flexi coupling is fitted with the Vetus stern gland.

 

The engine mounts are flexible, the Vetus stern gland is flexible, and any other flexible element in line will make the shaft oscillate.

[Guest]

It is not recommended that a flexi coupling is fitted with the Vetus stern gland.

 

The engine mounts are flexible, the Vetus stern gland is flexible, and any other flexible element in line will make the shaft oscillate.

Yes I got the same advice from Vetus some years ago, as did various one-time members, though oddly the Vetus agent fitted one in my boat! The shaft certainly oscilates when in reverse on my boat, and has done since new.

Recently I was rather abruptly told by a member that " I have contacted Vetus and this isn't so" so I am not certain about this situation now. Some have them, some don't. I have seen a few Liverpool boats with Vetus stern gear and no flexible installed, with many hours on the clock.

Edited May 1, 2015 by Guest

[Timleech]

Yes I got the same advice from Vetus some years ago, as did various one-time members, though oddly the Vetus agent fitted one in my boat! The shaft certainly oscilates when in reverse on my boat, and has done since new.

Recently I was rather abruptly told by a member that " I have contacted Vetus and his isn't so" so I am not certain about this situation now. Some have them, some don't. I have seen a few Liverpool boats with Vetus stern gear and no flexible installed, with many hours on the clock.

 

It seems to be common to fit an R&D semi-flexible coupling along with Vetus sterngear.

I did a job a few years ago for a customer who had suffered multiple gearbox failures, eventually narrowed down to having a flex coupling with Vetus sterngear. Not sure, that might have been a Centaflex coupling, honestly can't remember.

He seemed to go away happy (and not return!) with new gearbox and solid connection to prop shaft.

 

Tim

[bizzard]

It's nice to have some kind of flexible coupling though even if semi flexible for when the prop clouts something solid it will slightly lessen the sudden sharp jolt on the gearbox. Liverpool boats that I've worked on some had non and some did have the R&D flex coupling and the couple of non Liverpool boats I've worked with Vetus sterngear had the R&D fitted.

My boat has a solid mounted Lister ST2 and LH150 box. I fitted a Ford Granada propshaft rubber doughnut coupling years ago £10 they fit perfectly having 6 holes which you use 3 and 3. 3 bolts to the gearbox h/coupling and 3 bolts to the shaft h/coupling with a few spacer washers to prevent buffering up.

So anyone looking for a flexible coupling for the same, the Granada doughnut is ace.

Edited May 1, 2015 by bizzard

[Guest]

 

It seems to be common to fit an R&D semi-flexible coupling along with Vetus sterngear.

I did a job a few years ago for a customer who had suffered multiple gearbox failures, eventually narrowed down to having a flex coupling with Vetus sterngear. Not sure, that might have been a Centaflex coupling, honestly can't remember.

He seemed to go away happy (and not return!) with new gearbox and solid connection to prop shaft.

 

Tim

That is how mine was supplied and fitted.

I wonder if other factors such as propshaft length affect this?

It's nice to have some kind of flexible coupling though even if semi flexible for when the prop clouts something solid it will slightly lessen the sudden sharp jolt on the gearbox. Liverpool boats that I've worked on some had non and some did have the R&D flex coupling and the couple of non Liverpool boats I've worked with Vetus sterngear had the R&D fitted.

My boat has a solid mounted Lister ST2 and LH150 box. I fitted a Ford Granada propshaft rubber doughnut coupling years ago £10 they fit perfectly having 6 holes which you use 3 and 3. 3 bolts to the gearbox h/coupling and 3 bolts to the shaft h/coupling with a few spacer washers to prevent buffering up.

So anyone looking for a flexible coupling for the same, the Granada doughnut is ace.

Is that similar to the Hillman Imp type doughnut, Biz?

[bizzard]

That is how mine was supplied and fitted.

I wonder if other factors such as propshaft length affect this?

Is that similar to the Hillman Imp type doughnut, Biz?

Yes similar but the Hillman Imp and Lotus Elan were smaller, so too small.

[Guest]

Yes similar but the Hillman Imp and Lotus Elan were smaller, so too small.

Cheers Biz. Interesting idea. were the hole centres just right for your couplings?

Edited May 1, 2015 by Guest

[bizzard]

Cheers Biz. Interesting idea. were the hole centres just right for your couplings?

Yes, exactly. So anyone with a LH150 or LM100 gearbox with or without the Lister reduction gear and has 6 bolt half couplings the Ford Granada prop shaft doughnut is the biz.

[Guest]

Yes, exactly. So anyone with a LH150 or LM100 gearbox with or without the Lister reduction gear and has 6 bolt half couplings the Ford Granada prop shaft doughnut is the biz.

Good stuff. A good saving there over a "marine" coupling

[bizzard]

Good stuff. A good saving there over a "marine" coupling

Your telling me, and probably a lot superior.

[blackrose]

If you had to push the coupling downwards, sounds like the engine has gone out of alignment, likely the engine mounts have settled. Did you fit new locknuts on the half coupling?

 

I'm not sure about this? I might be completely wrong, but isn't there the possibility that he had to push down on the shaft by 2 or 3mm to get it back into the coupling simply due to the weight of the prop on the other end?

 

There is a certain amount of flexibility in Vetus stern gland after all.

 

Anyway it should be easy enough to check the alignment using a feeler gauge on the R&D coupling. I got some instructions with mine but I'm sure they're also published online.

Edited May 2, 2015 by blackrose

[Guest]

I'm not sure about this? I might be completely wrong, but isn't there the possibility that he had to push down on the shaft by 2 or 3mm to get it back into the coupling simply due to the weight of the prop on the other end?

 

There is a certain amount of flexibility in Vetus stern gland after all.

 

Anyway it should be easy enough to check the alignment using a feeler gauge on the R&D coupling. I got some instructions with mine but I'm sure they're also published online.

I see your point, and I think one answer would be that it depends on the length of the shaft, prop size and the diameter of shaft which might affect the point of balance. So hard to say with such things when not present. On my particular boat, with the half coupling in place on the shaft, it tends to drop slightly from the engine when unbolted (engine alignment correct.) I can see that under different circumstances that this may not always be the case.

The feeler gauge method on the R&D is great for doing an annual check etc., but for proper aligmnet setting it is necessary to clamp the shaft at dead centre of the sterngear (vertically and horizontally,) using a piece of angle iron and a car exhaust clamp, then check engine alignment as if it were a conventional stern gear with solid bearing. The R&D is then popped back into place, and the feeler gauge method will show any slight deviation. This may sound long winded, but was necessary for me after the engine mounts came loose and lost their adjustment completely.

I am no expert, but have found this to be the easy way of doing things.

Edited May 2, 2015 by Guest