Peculiar noise coming from prop shaft.

ferrispeterchris

ferrispeterchris

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While out sailing the other day heard a noise which I first thought was slopping from the cockpit drains.I then realised that it was too regular to be that and found it came from the prop shaft which was "free wheeling".When I had moored up I investigated further initially thinking of a dry Cutlass (?) bearing even though I regularly tighten the grease thingy. Discovered when I turn the shaft by hand the rubbing noise is coming from the engine end where the shaft enters the gearbox.
I have recently got caught up twice by lobster pot ropes (not while motoring) once a heavyish rope which was round the rudder and I hacksawed off and then by a lightish one which freed itself.What is worrying me is the thought that the heavier one might have pulled the propellor. There does not appear to be any water coming or oil going out from the gearbox. Anyone had this happen to them? Peter.
 
Hmmn..interesting! Is the noise there in both forward and reverse? Is there any resistance when turning the shaft by hand in one spot. Stupid one I know but have you checked your gearbox oil level? Have you got a flexi/coupling between gearbox and prop? You mentioned that you weren't motoring when you caught the ropes, so I'm hoping excessive strain wasn't put on the output shaft. Are there any signs of slippage on the coupling...what gearbox do you have by the way? Lot's of questions I know but it's hard to guess from afar.

www.carpentersw.com
 
Prop shaft does not seem to be mis-aligned.Gearbox is hydraulic I believe.I did notice that a couple of the ball shaped thingies that connect both plates seem to be pulled out more than the rest.It makes a scraping noise whichever way I turn the shaft.The "rubbing" only happens over half a revolution then free.Turns OK mind you, no significant friction/resistance.I am just wondering if there is an oil seal on the shaft where it leaves the gear box which might have been damaged. Peter.
 
Peter, I'd go for the simple stuff first. You say "I did notice that a couple of the ball shaped thingies that connect both plates seem to be pulled out more than the rest" I'd say the chances are that the coupling has been strained/distorted and therefor the alignment will be out. Most output shaft oil seals are pressed into the housing and unless the seal has somehow moved and is rubbing on the gearbox end coupling, I'd say this is probably not your problem. It sounds like the flexi-coupling has taken the brunt of any shaft resistance and is distorted.
 
Thanks once again.Do you know of any way to reverse this damage?For example where could the damaged "balls" be bought if that is to be the solution? (Or could they be compressed back into shape?) Peter.
 
ferrispeterchris said:
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First attempt at adding photos. I have been told that replacement round rubber thingies are a terrible price and the way to go is a nylon flexible coupling from ASAP. Peter.
Click to expand...

They look the same as the couplings that failed twice on my Centaur, the second occasion being a major contributary factor in the loss of my boat. I think they were about £100 for four. I don't know if the nylon coupling would be any more rubust, but I wouldn't be happy with the original type of coupling ever again.
 
These look like the std volvo type couplings
the rubbers can be replaced individually or as suggested fit the R&D from ASAP
youl need to give engine+gearbox details but then it is a simple one for one replacement
 
Just a quick note.
The grease you pump in is unlikely to be designed to lubricate the cutless/stern tube bearing. The bearings aft of the seal are in most cases designed to run with water as the lubricant.

If you pump in too much grease the grease can block the water channels in the bearing which will lkead to it overheating/wearing/seizing.

Grease is a poor conductor of heat.
 
Hi went back and read post
it is likely that you would break a rubber getting a rope round the shaft
if one rubber goes then it throws the coupling out of balance so you you will need to replace the damaged rubbers about £30 each or £120 complete unit but the R&D nylon from ASAP etc will be neareer £40
change it before you use the boat again
if it breaks in reverse which it most likely the prop and shaft will pull back and may do a fair bit of nasty
 
Hey nice photo's Pete...now we can see what's been going on. As the guy's have said go for a complete new R&D coupling from ASAP. They are a very helpful and knowledgeable bunch and if you give them your exact details I'm sure they'll come up with the goods. Just one thing...when you take the coupling off, have a look at the end of your gearbox and see if it's been catching on it. In one of the pics that I blew up to get a better look there seems to be a bit of distortion in the back-plate nearest the box.
 
I was in touch with ASAP and as you say they are very helpful.Mind you they wanted to know all sorts of odd things like the step down ratio of the gearbox and whether the coupling at the gearbox end had a "dome" on it - all I can see is a big nut.Curiously enough I contacted R&D who were also very quick to reply and very helpful but they were slightly dearer than ASAP and they make them!I think I will buy the nylon one,should that fit on to the smaller 4" flange (in Photos)?
 
r + D

the R&D coupling comes in different grades depending on the torque or HP/REVS
I asume you have a volvo engine but the gearboxes vary and some use bolts but others setscrews
give as much info as you can
go to R+D website look up 910-019 which is typical
 
ferrispeterchris said:
Thanks once again.Do you know of any way to reverse this damage?For example where could the damaged "balls" be bought if that is to be the solution? (Or could they be compressed back into shape?) Peter.
Click to expand...

The coupling needs to be replaced. You might also consider the Bullflex coupling from Vetus. much more expensive but much better.

You also need to think about dealing with the underlying cause of the problem, which was almost certainly getting rope around the prop. Therefore fitting an effective rope cutter should be on your list as well.
 
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