prop shaft coupling???

[Tranona]

Yes, the prop is too big with that gearbox ratio. The 2.6:1 will slow the shaft speed down and allow the engine to rev higher.

Went through the same problems with stern tubes when I fitted my 1GM. The choice is having a rigid coupling and allowing the shaft to float, or introducing a bearing in the tube and a flexible coupling. You need to determine the clearance in the tube if you are using a fixed coupling and make sure the shaft is central in the tube when the engine is aligned. Even then unless you have lots of clearance the shaft can still touch the sides. This may be the source of your whirring noise. In my installation I was able in the end to fit a cutless bearing in the inboard end of the stern tube using the old stuffing box housing, a Volvo seal and a Bullflex coupling. All works well. The Volvo seal is good as it is actually a water lubricated bearing and if you set it up correctly with the shaft central in the tube it provides good support to the inboard end and reduces the chances of the shaft rubbing on the sides of the tube. You may also find an R&D coupling helpful as it is more rigid than a Bullflex and does smooth out some of the movement, even with a floating shaft.

 

[mtb]

even though a single cylinder will move a little how much depends on the hardness or shore that the mounts are, plus of course any flex being imposed due to poor fitting and miss alignment
take a look on this web site http://www.avindustrialproducts.co.uk/ they make mounts and give plenty of information.
I'd not let a retard like the person who broke that fitting near an exhaust system on me boat !!! NO WAY it could kill you if that exhaust system isn't right
how the hell can you expect any thing but problems
They clearly don't know what their doing, I don't think they have aligned the engine/gearbox up to the shaft, if your getting adverse noise and vibration at the level you describe do not use it get legal advice and find a new yard

cheers
mick

 

[boatmike]

The answer is not as simple as yes/no. It depends on the distance between bearings on the propshaft, how much room between the engine flange and the rear bearing or stuffing box, and as others have said, the type of mounts. It also depends on whether or not you have a rear thrust bearing on the shaft. If the mounts are relatively hard, the distance between bearings is fairly long (assuming there are only two) then you should not need a flexible coupling. Conversely, as I suspect in your case, there is no thrust bearing and the thrust is taken on the engine, the bearings are fairly near one another, and there is room to fit one, a flexible coupling will help considerably. Your installers suggestion that you shouldn't fit a flexible coupling unless you have a plummer block to take the thrust is rubbish. Talk to R&D couplings. Their couplings will easily take the thrust and the "pull" in reverse on a floating shaft set up and are designed for this use. It does however sound as if your setup needs re-aligning, and if it were me I would check the alignment WITH THE BOAT IN THE WATER (which may well be different ashore) and fit an R&D coupling when doing so.

p.s. Seem to have crossed posts with Tranona. Just for the record his is also good advice if it applies in your case but you can, as I said, still have an R&D coupling with a floating shaft. Difficult to advise without more information on your setup.

 

[Malish]

Reading this thread, I end up with the view that you need an independent assessment from a surveyor to either kick the installer into doing a professional job or form the basis for a claim against them. It may cost as couple of £100 for the report but I have a hunch this will be money well spent in comparison to the minefield you will enter if trying to sort this mess out for yourself.

 

[Mel]

I have a 1GM10 in my boat and it was there when I purchased it over 10 years back. The engine had only done 50 hours at that time. I was then, new to boat ownership and considered the drive system to be excessively noisy. Also seeing it jump about was of concern to me. The engine ran fine and did push my 5 ton, 24 ft. yacht at approx. 5.5 knot , which was fine.

I enquired at French Marine and was told that the Yanmar 1GM10 should not be fitted with a flexible coupling.
I ignored this and fitted an R&D coupling when ashore and did my own shaft alignment.

The engine now has 900 hours on the clock and runs fine - I still think it is noisy and does jump about a lot at low revs. The R&D flexible coupling certainly has done no harm - I fitted a traditional stuffing box gland at the same time and all works very well as far as I can judge. I do think that there is some improvement

It should be noted that I have no sound insulation and the level of noise is probably normal under these circumstances. I do drop revs to use the radio !

 

[surekandoo]

Reading this thread, I end up with the view that you need an independent assessment from a surveyor to either kick the installer into doing a professional job or form the basis for a claim against them. It may cost as couple of £100 for the report but I have a hunch this will be money well spent in comparison to the minefield you will enter if trying to sort this mess out for yourself.

Yes that's the conclusion I've come to belatedly. I have contacted the RYA's legal department by email and am awaiting a response. I have no intention of fiddling with it myself. I've paid for a professional installation and that's what I expect and am entitled to receive.

 

[sailorman]

Yes that's the conclusion I've come to belatedly. I have contacted the RYA's legal department by email and am awaiting a response. I have no intention of fiddling with it myself. I've paid for a professional installation and that's what I expect and am entitled to receive.

where are the so called engineers based

 

[ParaHandy]

Conversely, as I suspect in your case, there is no thrust bearing and the thrust is taken on the engine, the bearings are fairly near one another, and there is room to fit one, a flexible coupling will help considerably

This is such good advice. I have a 3GM which is probably not as bad as yours but feels, if you're an engineer, wrong. It's been like that for over 12 years so it might not be harming anything; just everything else has to be screwed down, hard!

 

[Malish]

where are the so called engineers based

doubt the OP wants to answer that atm.

 

[surekandoo]

doubt the OP wants to answer that atm.

Correct but there are clues for those with an investigative bent!

 

[sailorman]

Correct but there are clues for those with an investigative bent!

Very local then

 

[surekandoo]

Yes, the prop is too big with that gearbox ratio. The 2.6:1 will slow the shaft speed down and allow the engine to rev higher.

Went through the same problems with stern tubes when I fitted my 1GM. The choice is having a rigid coupling and allowing the shaft to float, or introducing a bearing in the tube and a flexible coupling. You need to determine the clearance in the tube if you are using a fixed coupling and make sure the shaft is central in the tube when the engine is aligned. Even then unless you have lots of clearance the shaft can still touch the sides. This may be the source of your whirring noise. In my installation I was able in the end to fit a cutless bearing in the inboard end of the stern tube using the old stuffing box housing, a Volvo seal and a Bullflex coupling. All works well. The Volvo seal is good as it is actually a water lubricated bearing and if you set it up correctly with the shaft central in the tube it provides good support to the inboard end and reduces the chances of the shaft rubbing on the sides of the tube. You may also find an R&D coupling helpful as it is more rigid than a Bullflex and does smooth out some of the movement, even with a floating shaft.

There's a space issue. There is only 25mm between the outboard end of the shaft coupling half and the start of the brass shaft seal. An R & D coupling for the 1GM10 is 32.5mm long!

I don't think it's possible to buy a more compact seal than the one I've got which is an oil fed brass tube with lip seals in either end clamped to the thick wall rubber tube which is in turn clamped to the stern tube. So it looks as though I'm stuck.

 

[Tranona]

There's a space issue. There is only 25mm between the outboard end of the shaft coupling half and the start of the brass shaft seal. An R & D coupling for the 1GM10 is 32.5mm long!

I don't think it's possible to buy a more compact seal than the one I've got which is an oil fed brass tube with lip seals in either end clamped to the thick wall rubber tube which is in turn clamped to the stern tube. So it looks as though I'm stuck.

Have a look at the Volvo (or Radice) seal. Only 110mm long - Almost certainly shorter than your existing arrangement. The Vetus bearing which is of the type you have is 144mm long by comparison. Have the same problem of space in my installation. A Bullflex coupling is 85mm long plus 10mm for the adaptor to fit the Yanmar gearbox output flange. From memory a bit shorter than the combined length of a Yanmar coupling and an R&D. As you may have guessed I have been through all the combinations of couplings and shaft seals and the Bullflex/Volvo combination takes up the least space.

 

[boatmike]

Have a look at the Volvo (or Radice) seal. Only 110mm long - Almost certainly shorter than your existing arrangement. The Vetus bearing which is of the type you have is 144mm long by comparison. Have the same problem of space in my installation. A Bullflex coupling is 85mm long plus 10mm for the adaptor to fit the Yanmar gearbox output flange. From memory a bit shorter than the combined length of a Yanmar coupling and an R&D. As you may have guessed I have been through all the combinations of couplings and shaft seals and the Bullflex/Volvo combination takes up the least space.

Also consider moving the engine mounts forward on the bearers if there is room........

 

[fisherman]

I wonder if you would be better with a rigid mounted engine. The shaft is absorbing the flexing between the coupling and aft stern tube bearing, and with a rigid coupling, even with an R&D it must be considerable stress on the shaft. One way might be to mount the engine on a raft, steel angle iron or channel iron which itself is mounted on 3 or 4 flexible mounts each side, to cut down on vibration. I often wonder if a stabiliser bar could be used, mounted from the top of the engine to the side with rubber bushes, as was on the Mini. Your engineer talks about a plummer block/thrust bearing, this would be for a GKN Aquadrive type of installation, for which you have not the space.

 

[surekandoo]

I wonder if you would be better with a rigid mounted engine. The shaft is absorbing the flexing between the coupling and aft stern tube bearing, and with a rigid coupling, even with an R&D it must be considerable stress on the shaft. One way might be to mount the engine on a raft, steel angle iron or channel iron which itself is mounted on 3 or 4 flexible mounts each side, to cut down on vibration. I often wonder if a stabiliser bar could be used, mounted from the top of the engine to the side with rubber bushes, as was on the Mini. Your engineer talks about a plummer block/thrust bearing, this would be for a GKN Aquadrive type of installation, for which you have not the space.

As a mini owner myself many years ago, I'd also thought about some sort of stabiliser bar on the top of the engine.

I think I need to be patient & let the "professionals" sort the problems out. They have reported back today that they have realigned the prop shaft in the stern tube and then realigned the engine to the prop shaft. They report that the mechanical whirring noise has vanished.

They claim to have got 2950rpm out of the engine and claim the boat is reaching hull speed in flat water.

Will go down and test next week weather permitting.

 

[surekandoo]

Have a look at the Volvo (or Radice) seal. Only 110mm long - Almost certainly shorter than your existing arrangement. The Vetus bearing which is of the type you have is 144mm long by comparison. Have the same problem of space in my installation. A Bullflex coupling is 85mm long plus 10mm for the adaptor to fit the Yanmar gearbox output flange. From memory a bit shorter than the combined length of a Yanmar coupling and an R&D. As you may have guessed I have been through all the combinations of couplings and shaft seals and the Bullflex/Volvo combination takes up the least space.

That's most helpful. Please see my reply to fisherman. Installers are dead against any sort of flexible coupling as the claim it will allow the engine to flex more. Like I say I have to remain patient....

 

[Pye_End]

It is good that they have not washed their hands of it, and are getting better results.

It is also disappointing that they did not align the engine properly when it was installed and does not inspire confidence. As far as rpm is concerned, unless you are achieveing near full rpm you will not be using all the hp of the engine available. In flat water you may get good boat speed, but when the chips are down you will lament the lost rpm and lost hp.

 

[Tranona]

As a mini owner myself many years ago, I'd also thought about some sort of stabiliser bar on the top of the engine.

I think I need to be patient & let the "professionals" sort the problems out. They have reported back today that they have realigned the prop shaft in the stern tube and then realigned the engine to the prop shaft. They report that the mechanical whirring noise has vanished.

They claim to have got 2950rpm out of the engine and claim the boat is reaching hull speed in flat water.

Will go down and test next week weather permitting.

Not my experience. You will see many 1GMs with flexible couplings. The issue is more about clearance in the stern tube. I kept the original Stuart Turner stern tube, mainly because it was impossible to remove it from the deadwood without major work and the inside bore is only 1 1/4" with a shaft diameter of 1" only leaves 1/8" clearance! I think glass tubes have more clearance so accommodate a bit more movement. Fortunately I was able to put the bearing in the inboard end so the shaft is automatically in the centre and does not move. However before I did that mod I ran with an R&D and no bearing and the coupling dealt with a lot of the engine movement without affecting the shaft.

Difficult to say what would work without trying, but if it were my boat I would go down the Bullflex/Volvo route. Expensive experiment but if it works it will be worth it.

If they say it will get 2950, then reducing the prop pitch by 1" will take it up to 3300 at least which is at the bottom end of the recommended range. Changing the gearbox to a 2.6 will, I think have a similar effect without changing the prop.

 

[Old Troll]

For information I have 27ft yacht with a Yanmar 1GM10 installed. The gearbox is the KMP 2.62 witha 14" x 9" two bladed propeller of ancient vintage. There is R & D coupling fitted with a PSS shaft seal and flexible engine mounts. All has been running for years without problem and I believe is a standard set up for such engine instalations apart from perhaps the choice of shaft seal. Hope this helps in what should really be a simple engine instalation.