Engine/box/propshaft angle

[Superflid]

Currently (Slowly!) fitting an engine and box into my old 27 foot wooden fishing boat and have a question.
Does the engine and box have to be in line (vertically) with the propshaft, or is some degree of angle acceptable?
There are 2 UJ's on the connecting shaft between the gearbox and propshaft so there is scope for a large angle. Obviously it would be easier on the joints the closer they were aligned but this is not 100% possible.
Engine is actually an old Landrover 2.25 diesel (were talking budget boating here!) and a driveplate has been made up professionally (read "expensively....) and it's bolted up solidly to the gearbox.
Is a larger angle going to cause me problems I'm not expecting?

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[omega2]

Speaking purely Ford (Sabre,Mermaid) the max angle with a front well sump is 15 degrees.

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[30boat]

What is taking the load from the prop?Do you have a thrust bearing?UJs are not designed to take axial loads,or am I wrong?

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[boatmike]

The key thing to ensure is that the propshaft and engine crankshaft are in the same plane. i/e parallel to one another in both axes (vertical/ horizontal) This will ensure that the two U/Js are running at a contant speed at the same angle to one another. The maximum angle they are recommended to work at is usually around 5 degrees. I have seen this exceeded but usually rapid wear will be caused due to axial loads. Hope this is clear. This assumes they are simple U/Js not CV joints. PM me if you need further info.

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[boatmike]

No they are not designed to take axial loads. you are not wrong. Also your question re thrust bearing is valid. Ideally with simple UJ's the load should be taken on a thrust bearing mounted on the propshaft. CV joints (like Halyard supply) are different. I am assuming we are not talking about these here.

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[boatmike]

Yes that's typical of most diesels but the question was related to relative shaft angles and UV joints and that's a different consideration.

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[Superflid]

Thanks for that. I can arrange things so they are parallel in both planes.
Re the thrust bearing.
What, how?
I'm relatively new to boating, totally new to inboard engines, so this is something I've not come across.
There is about 8 - 10 inches of bare shaft available between the packing gland and the coupling. I assume that I'll be needing something to fit here to take the thrust.

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[boatmike]

OK Ken, lets take this a step at a time as we might have some terminology problems here. Can you answer the following questions please.
These "UJ's" What do they look like? Where did they come from? Are they like the UJ's on the end of the propshaft of your car or are they in fact something else?
Secondly, are you fitting a new engine into a boat that previously had a different one fitted or what? What was the previous setup like and are these joints left over from that or something you have added? Is it not possible to get the engine crankshaft in line with the drive shaft regardless of how big an angle that might be at present? If not why not?

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[Superflid]

Thanks for the help Mike.

Yes, the UJ's are car type (actually lorry, the last owner told me. He had the shaft made up.)
The shaft with the UJ's was left from the last engine installation. The owner had gone through 3 different engines. A Lister twin which died of old age, a BMC diesel which lost it's oil through a failed seal,and finally a Ford petrol (which he wanted to keep)

It might well prove posssible to line up the propshaft and crankshaft, this would be ideal. My point in asking was to give me any available options which might make things easier. I'll be going to the boat tomorrow so can take some measurements.

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[boatmike]

OK Ken it's clearer now. I have very much in mind that you are on a budget so here are my thoughts. It sounds as if the arrangement is the previous owners "ersatz" solution to a problem that may fly in the face of good practice.
UJ's are not designed to take thrust at all but you might get away with using them if the shafts are pretty much in line as the loads are in fact relatively low. I don't like it though and would advise getting rid of them if you can. Bulkhead mounted thrust bearings are expensive and with 2 UV's and a thrust bearing you just have more things to maintain.
I would prefer to see the shaft continuous from the prop up to the gearbox with a normal flexible coupling on the gearbox flange. This will require you to mount the engine pretty accurately in line and possibly replace the current shafts with a solid one. As I assume you have a flange already on the end of your propshaft proper however it would not be a bad thing to have a flexible mount on that and another on the engine to absorb any misalignment provided that there is a proper bearing on the forward end of the propshaft. I have a horrible suspicion that what you might find however is that the inboard bearing is simply a water seal. If it is I would advise that you either get a new shaft made up and get the engine in line or replace that bearing with a solid bulkhead mounted one. But still try to get the shaft as well in line as you can with either arrangement.
When you go to the boat tomorrow examine the "bearing" on the forward end of the propshaft. If it is clearly a solidly mounted plain bearing mounted directly to the structure without any bits of rubber or flexible thingys then we have the choice if fitting a number of things forward of this. If it is a flexible water seal it will be obvious I think as it will be designed to allow the shaft to move axially to compensate for movement at the engine end. If its a water seal and you CAN get the engine lined up by far the best arrangement would be a new shaft. Expensive to an extent but cheaper than the alternatives. If you CANT get the engine lined up and it is a solid bearing we need to know how far out of alignment it is. One final thought. If the boat is out of the water and the shaft is in place try shoving the prop towards the pointy end of the boat and see if it meets resistance. I might be misjudging the previous owners design and it might be a thrust bearing already!
If it is then we should not only have a thrust bearing but find we have a spline on one of the UV joints to allow longitudinal movement. I hope this is all clear. If not PM me and I will give you my phone number... And don't worry, I only charge people for advice if their boat is over 40 ft


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[Superflid]

It's becoming clear Mike!

The propshaft can be moved back and forward easily, so it's fairly obvious there's no thrust bearing.
Pound signs kept flashing in front of me when "new shaft" was mentioned.
Then I remembered........

I originally had an old aluminium boat given to me just over a year ago (my first boat), I think the owner was glad to see the back of it! After some stripping work it was obvious that it would never be seaworthy without some extensive (expensive) work to corroded rivets and plates below the waterline.
The decision was taken and it was scrapped.

Being a bit of a hoarder, as much as possible that looked useful was kept.

Just had a look at the shaft from that boat. Drive flange, large thrust bearing, packing gland and nut all still in one piece. Tried the spare prop I have here from my boat and it fits! I may have a replacement shaft complete with thrust bearing, will have to check on length tomorrow but seems long enough.

Back tomorrow with the next installment................

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[boatmike]

Sounds good Ken. Everything comes to him who hoards..... Good luck with it and let me know how you get on.

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[Superflid]

Right, back from the flatlands of Lincolnshire......

Some bad news, mostly good.

First off, the spare shaft I have is too short. At least six inches, plan A down the pan!

However!

The Thrust (I assume) bearing on the spare shaft is fitted by means of a sleeve over the shaft to which it is fixed (shrunk on or welded?). There are 2 bolts which go through this sleeve, the shaft (obviously) and the drive flange on the end of the shaft. The bearing is housed in a large pedestal type housing which can be bolted down. This would both prevent fore and aft movement and support the propshaft itself.

I've removed it from the old shaft in preperation for cleaning and regreasing. I can fit it to my boat propshaft in situ, leaving me with matching flanges on the gearbox and propshaft. This is where I assume the flexible coupling needs to be.

On the original engine/gearbox/prop lining up question, there are still the remains of the last engine supports. These have been built to match the slope of the prop, meaning that it will be easy to line things up.

Now, has anyone got a flexible coupling with a PCD of three and one eights of an inch they are giving away.........

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[boatmike]

OK. Lets recap and make sure I have this right. You are intending to fit the thrust bearing that you have found to the existing shaft. When you have done this the shaft will terminate in a flange forward of a fixed shaft bearing that has a built in thrust pad and has no flexible mounting. In other words it won't move sideways at all? I am assuming you also have a waterseal (stuffing box or something) somewhere on the shaft which will end up aft of this thrust bearing to keep the water out? If so the problem is to transmit power to this flange without interfering with the thrust bearing. This would in fact ideally be achieved with your intermediate shaft that has UJs on it. BUT and it's a big BUT you MUST have a splined end or some such arrangement to ensure the shaft length can change with the movement of the engine. Otherwise you will definitely knacker the UJs and/or the thrust bearing as they will be fighting one another.
EITHER the thrust must be taken on the gearbox OR on the thrust bearing. Not both. Furthermore you MUST NOT have a flexible coupling on either the gearbox end or the thrust race end if you are using UJs or the shaft will vibrate like the clappers.
SO
You either need to forget the thrust race and go with a flexible waterseal on the shaft with the shaft going all the way back to the gearbox terminating in a flexible coupling (which would be entirely conventional letting the gearbox take the thrust), or fit your thrust bearing very rigidly retaining the existing waterseal and use the intermediate shaft you have already, provided that one end is splined. If it isn't don't use it.
There are two other possibilities you could consider if you don't want to pay for a new shaft. Both assume the engine can be lined up with the propshaft. First, simply move the engine aft to meet the shaft. Second, have a shaft extension made to make up the distance you are short with a flange on both ends. Frankly it sounds to me that you are in danger of solving one problem and creating another if you are not careful. Frankly, if you are only 6ins short I would move the engine back. If you can't do that get a quote on a new shaft. You might find its cheaper than trying to compete on "scrapheap challenge"!
Either way I will send you a PM with my phone no as it might be easier to talk it through on the phone if you have any other questions.


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[Superflid]

OK. Lets recap and make sure I have this right. You are intending to fit the thrust bearing that you have found to the existing shaft. When you have done this the shaft will terminate in a flange forward of a fixed shaft bearing that has a built in thrust pad and has no flexible mounting. In other words it won't move sideways at all? I am assuming you also have a waterseal (stuffing box or something) somewhere on the shaft which will end up aft of this thrust bearing to keep the water out? If so the problem is to transmit power to this flange without interfering with the thrust bearing.
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That would have been the idea.......

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This would in fact ideally be achieved with your intermediate shaft that has UJs on it. BUT and it's a big BUT you MUST have a splined end or some such arrangement to ensure the shaft length can change with the movement of the engine. Otherwise you will definitely knacker the UJs and/or the thrust bearing as they will be fighting one another.
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Shaft has no spline.
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EITHER the thrust must be taken on the gearbox OR on the thrust bearing. Not both. Furthermore you MUST NOT have a flexible coupling on either the gearbox end or the thrust race end if you are using UJs or the shaft will vibrate like the clappers.
SO
You either need to forget the thrust race and go with a flexible waterseal on the shaft with the shaft going all the way back to the gearbox terminating in a flexible coupling (which would be entirely conventional letting the gearbox take the thrust),or fit your thrust bearing very rigidly retaining the existing waterseal and use the intermediate shaft you have already, provided that one end is splined. If it isn't don't use it.

There are two other possibilities you could consider if you don't want to pay for a new shaft. Both assume the engine can be lined up with the propshaft.
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First, simply move the engine aft to meet the shaft. Second, have a shaft extension made to make up the distance you are short with a flange on both ends.
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Does this mean that it would be feasable to use the bearing and mount it solidly, then move the engine back to meet the shaft and connect the two solidly? The flanges would mate. Engine movement would seem to be a problem.
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Frankly it sounds to me that you are in danger of solving one problem and creating another if you are not careful. Frankly, if you are only 6ins short I would move the engine back. If you can't do that get a quote on a new shaft. You might find its cheaper than trying to compete on "scrapheap challenge"!
Either way I will send you a PM with my phone no as it might be easier to talk it through on the phone if you have any other questions.
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I'm happy to talk it through here Mike, I'll PM you the reason for that.....
There is no real rush on this, the project will be completed over the winter. If I can get to the boat once a fortnight I'm doing well!

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[boatmike]

Please answer the following

1. Without changing anything what sort of bearing do you have on the propshaft at the moment? Does it allow sideways movement (flexible mounted) or not?

2. If you remove the intermediate shaft complete with UJs what distance do you have between the engines gearbox flange and the existing flange with the present shaft?

3. If you remove the present shaft and fit the other shaft you have in the present bearing does it fit and what is the distance between the flanges then?

$. How far back can you move the engine ?



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[Superflid]

1. Without changing anything what sort of bearing do you have on the propshaft at the moment? Does it allow sideways movement (flexible mounted) or not?

There is a "stuffing box" at the inboard end, I assume there is a bush at the prop end. No other bearing that I know of.

2. If you remove the intermediate shaft complete with UJs what distance do you have between the engines gearbox flange and the existing flange with the present shaft?

Engine still sat on my drive at home, so about 70 miles! Sorry, my sense of humour... (See 4. below)

3. If you remove the present shaft and fit the other shaft you have in the present bearing does it fit and what is the distance between the flanges then?

I'm pretty sure that the spare shaft isn't long enough to reach much further than the stuffing box. (Please correct me if that's the wrong term for a boat, an identical system was used on the pumps I maintained "Dahn t' pit" years ago).

4. How far back can you move the engine ?

I'm pretty much free to put the engine anywhere required. Lots of open deck.

Sorry to have taken up so much of your time already Mike, thanks for the help so far.



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[boatmike]

You have still not told me if the existing bearing which you call a stuffing box (I understand the term) is purely that or a bearing with a stuffing box on the inboard side. The important thing is, does it allow the shaft to move so that if you bolt the end of the shaft to the engine it will allow the engine to rock on its bearers a small amount? I will assume it does. In this case your best option is to move the engine aft to attach to the flange via a flexible coupling.

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[Superflid]

Thanks again Mike, sorry about any misunderstanding.

There is a small amount of movement of the shaft in the stuffing box. (Next trip I'll investigate in detail).
I'll go for the suggestion you outline, at least it's a more "standard" setup than UJ's! Simpler and more reliable too which has to be a good thing......

I'll probably be back for more help with the boat, sooner rather than later.

Many thanks, it really is appreciated.

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