Gearbox & Alignment issues

CliveG

CliveG

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Hi All

Let me tell you of my on going battle with Sirenia's gearbox.
Sirenia has a Beta 10 engine.
The last season I had trouble getting forward gear to engage.
I finally decided to replace the Gearbox with a new TCM40P box from Beta as this is their recommended replacement.
Around Easter We pulled the engine out of its hole and installed the new box.
We put it all back together and checked the alignment - This seemed o.k. - the flange plate on the shaft slid onto the bolts of the flexible drive fine.
When we ran the engine in gear the it was rocking around quite alarmingly.
After some head scratching I thought that it could be weak engine mounts (one did look a bit sick) and I was aware that the cutless bearing was quite worn.
I had Sirenia hauled out and proceeded to change the engine mounts and the cutless bearing.
with some adjustment we got the gear box and shaft to match up.
I took the flexible coupling out and made sure that the was no gaps between the gearbox flange and the shaft flange and the bolts slipped in easily.
We relaunched last weekend and headed down river to the summer mooring.
Once on the move there was a heck of a banging from the prop shaft area.
As I had my car at the mooring I pressed on to there.
Over this week I have been trying to work out what is wrong and thought that there could be a mis-alignment with the boat afloat rather than on her trailer.
I have just checked the alignment again and found it to be as before.
The rear of the engine is still going round in circles.
The only thing I can think of is a bent prop shaft but it was quite o.k. with the old gearbox. (once you could get it into gear!).

Most likely heading back up river next weekend to get her out again. :(

Here is a video of the rear of the engine running at tickover in reverse (On a mooring so could not go ahead)
http://grounds.org.uk/Sirenia/Gearbox shake.mp4

Any thoughts would be welcome.
 
Last edited:
sailorman said:
did you centralise shaft in the tube prior to aligning the engine
Click to expand...

Hi Roger.

I tried to get it central but it would not move up as it needed to and it stayed in the same location when turned.
It has always been in that location in relation to the tube ever since I have had her.
 
CliveG said:
Hi All

Let me tell you of my on going battle with Sirenia's gearbox.
Sirenia has a Beta 10 engine.
The last season I had trouble getting forward gear to engage.
I finally decided to replace the Gearbox with a new TCM40P box from Beta as this is their recommended replacement.
Around Easter We pulled the engine out of its hole and installed the new box.
We put it all back together and checked the alignment - This seemed o.k. - the flange plate on the shaft slid onto the bolts of the flexible drive fine.
When we ran the engine in gear the it was rocking around quite alarmingly.
After some head scratching I thought that it could be weak engine mounts (one did look a bit sick) and I was aware that the cutless bearing was quite worn.
I had Sirenia hauled out and proceeded to change the engine mounts and the cutless bearing.
with some adjustment we got the gear box and shaft to match up.
I took the flexible coupling out and made sure that the was no gaps between the gearbox flange and the shaft flange and the bolts slipped in easily.
We relaunched last weekend and headed down river to the summer mooring.
Once on the move there was a heck of a banging from the prop shaft area.
As I had my car at the mooring I pressed on to there.
Over this week I have been trying to work out what is wrong and thought that there could be a mis-alignment with the boat afloat rather than on her trailer.
I have just checked the alignment again and found it to be as before.
The rear of the engine is still going round in circles.
The only thing I can think of is a bent prop shaft but it was quite o.k. with the old gearbox. (once you could get it into gear!).

Most likely heading back up river next weekend to get her out again. :(

Here is a video of the rear of the engine running at tickover in reverse (On a mooring so could not go ahead)
http://grounds.org.uk/Sirenia/Gearbox shake.mp4

Any thoughts would be welcome.
Click to expand...

As others have said, the coupling may be the problem, but two points: 1} you said you changed the engine mounts. Flexible engine mounts must be specific to the load/weight and natural frequencies of the engine so hopefully you obtained the correct mounts specified by the engine supplier. However, as you said the problem existed with both the old and new mounts this is unlikely to be the root cause although incorrect mounts can accentuate any frequency related problem. 2) some flexible couplings allow some radial missalignment (the type you get when the engine bounces up and down) and some do not. However, the type that allow radial missalignment must not be used with a propshaft that has a floating forward bearing (ie it has a flexible rubber hose between the tube and forward bearing like yours). With a floating forward shaft bearing and a coupling that allows radial misalignment the shaft\engine can whip about often resulting in the shaft hitting the inside of the propshaft tube. On some flex couplings, such as some Vetus ones there is a locating ring within the flex coupling that you either put in or remove depending on whether you have a floating shaft or not. Assuming your flex coupling worked perfectly with your existing floating shaft bearing when your old gearbox was working ??? then the only thing that could have changed is, if your coupling has a locating ring, did you refit it on reassembly?

Www.solocoastalsailing.co.uk
 
The prop is a quite new Brunton 2 blade Varifold that is in good condition.

The coupling is an R&D flexible nylon disc that is supplied as standard by Beta.
There is no coupling ring I am aware of.

The new engine mounts are from Beta as specified for this engine.

I think the only possibility is a bent shaft.
It didn't look bent when I was changing the cutless bearing ashore last week.
I can only assume that it got bent during the winter while the boat was on a drying pontoon mooring.

I am taking her back up river next week and will get her ashore again to see what I can find.
 
As sugested above,
uncouple the shaft flange and hand rotate the shaft checking for run out on the two facing plates.

I have had this happen. There was a grub screw on the shaft side of the coupling intended to stop any rotation between the flange and shaft. It had caused the very last 1" of the shaft to bend just a little.

A new shaft is cheap as chips if you find a local metal engineers.. bloody expensive if you buy it from Vetus.
 
Omega2
We get her ashore on her trailer the rear beam of which is under the engine location.
I have also put strop marker stickers on her to ensure that, if we lift her out that way we will miss the shaft, keel etc.

Scottie
I think the shaft would come forward enough to take the R&D out but when I clocked it with a dial gauge there did nos seem to be much movement of the flange on the end of the shaft.

I am getting her out on Saturday lunch time time.
We will see what we see then.
 
Looking at the video, it looks to me the problem is in the coupling.. / R&D. I am. ot familiar with an R&D. Is is possible it is not centric? Even a tiny bit will make the engine wobble.
 
I note some people are saying take out the R&D. In my experience it is much easier to check engine and shaft alignment with an R&D flexible coupling in place than it is to do it without - as long as you have fitted the specially machined bolt, used as the measuring point, in the right place. I believe there are some instructions available on/from the R&D website.
It is also my experience that in some older production boats the shaft log cannot reliably be expected to be parallel to the shaft.
When I experienced a knocking noise under way in my own boat it was because the engine was not properly aligned to the shaft AND the shaft wasn't centred as well as it could be in the shaft log.
 
Tomahawk said:
Looking at the video, it looks to me the problem is in the coupling.. / R&D. I am. ot familiar with an R&D. Is is possible it is not centric? Even a tiny bit will make the engine wobble.
Click to expand...

R & D are very helpfull & not far from you, give em a bell

Ah it was directed to Clive

R&D Marine Ltd.
Meadow Works
Clothall Road
Baldock
Herts
SG7 6PD
England
Telephone: +44 (0)1462 892391
Fax: +44 (0)1462 896448
 
Last edited:
When I suggested trying it without the R&D it was to eliminate the one part that could easily be removed assuming prop clearance allowed and could be done in the water.
The basic ABC of alignment is that only 2 out of 3 connections stern gland,mounts and coupling should be flexible although practically speaking the R&D disc is normally stiff enough to work ok.
 
Sirenia is now ashore.
I have used a dial guage to measure any movement of the shaft.
Against the P bracket there is no deflation as you turn the shaft.
2 feet forward of that where the shaft enters the stern tube there is about 1.5 mm of deflection.
Inside, between the stern gland and the flange to the flexible coupling there is about 1mm deflation.
This does not seem to be much but it is all I can find.
I can only assume that once the revs build up the shaft is deflecting more.

I will get on removing the engine tomorrow (again!) to get the shaft out.
It can't be drawn out to the stern as there is a skeg behind it.
 
Last edited:
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