Duo Prop Hub/Prop Separation

[Greg2]

Managed to take the boat out yesterday having hardly moved all season due to work and other commitments. Calm sea and sunshine meant an enjoyable run up the coast and a poodle around Scroby Sands to see the seals. Went to go on the plane for the return trip and something wasn't right as the starboard engine seemed to be struggling to reach full power and we only just managed to get on the plane. Port engine seemed fine and responsive with revs increasing on demand.

Spent today working through the starboard engine in a process of elimination to see what might be wrong before resorting to spending money on turbo, injectors, injector pump etc. We stripped the fuel system and blew through to ensure there were no blockages and were just putting things back together when one of the guys helping me spotted a gap between the cone and the rear prop on the port drive (unusually clear water meant they could be seen from the pontoon). To cut a long story short it turned out that the hub of the rear port prop had separated from the prop and the cone and prop had been rubbing and as a result taken metal off each other leaving a quarter inch gap. Haven't got the forward prop off yet but suspect it might be damaged to as there is some movement on it.

It looks as though there was never a problem with the starboard engine - it was working harder to make up for the port props not driving properly so no wonder the revs increased easily on that engine!!

Hopefully easily resolved with a spare set of props. I am hoping that no damage has been caused to the shafts or the drive - can't see how there would have been but would appreciate any thoughts on the matter.

The props were re-cons from a company on the Thames and had only done a couple of hours tops since I fitted them. No impact damage to the props so not sure how this happened.

Anyone else experienced this?

 

[Kawasaki]

A bit confusing!
But it sounds like the 'cush drive' in the bush of the prop has done its job
Did you get a kind of 'clutch slip' from the offending engine?

 

[Greg2]

A bit confusing!
But it sounds like the 'cush drive' in the bush of the prop has done its job
Did you get a kind of 'clutch slip' from the offending engine?

Sorry, didn't mean to confuse. In short the story about the starboard engine is not relevant - we thought there was a problem with it but there wasn't.

I think what you describe is what has happened i.e the hub turns but the prop doesn't. No signs of impact damage on the prop. Are you saying it is designed to do this in case of fouling/impact to protect the drive?

 

[DAKA]

The props were re-cons from a company on the Thames and had only done a couple of hours tops since I fitted them. No impact damage to the props so not sure how this happened.

Anyone else experienced this?

I havent experienced your issue but I was once forced into buying a secondhand set of duo props ( stuck in Belgium) and despite looking brand new they didnt last long but did get me home.

I carried 6 spare props in the end.

One of the blades off the 4 blades would regularly snap off ( every 1000 miles or so), being the outside prop I would change at sea and carry on.

The reason I needed a prop in Belgium was the outer prop and cone had dropped off.
I didnt get any push from the single prop that was left, it would help a little for berthing but no serious push which sort of halves backs up your theory.

 

[Peanuts]

Hi

This may not have any thing to do with your problem but did you check the stainless steel ring was fitted, do you know the one I mean? I am not talking about the large one with serations in the inner circumference that goes on first. I have know many people to fit new props not knowing about the smaller ring as it tends to stay in the prop hub and they are not supplied with the props.

 

[Greg2]

Hi

This may not have any thing to do with your problem but did you check the stainless steel ring was fitted, do you know the one I mean? I am not talking about the large one with serations in the inner circumference that goes on first. I have know many people to fit new props not knowing about the smaller ring as it tends to stay in the prop hub and they are not supplied with the props.

Not sure I know what you mean, which probably means the answer is "no"!! That said I have line cutters, which I think incorporates the spacer on the model I have.

 

[Peanuts]

Hi
Hope I have not confused you with my posting.

All I was trying to say was that I have seen several prop problems due to people leaving out either the main thrust washer on the 3 bladed prop and on the 4 bladed prop there is either a smaller thrust washer (stainless ring about 7/8" diameter) or as I believe in your case a line cutter, (older type) so if you have all of these fitted then this is not your problem.

 

[Greg2]

Hi
Hope I have not confused you with my posting.

All I was trying to say was that I have seen several prop problems due to people leaving out either the main thrust washer on the 3 bladed prop and on the 4 bladed prop there is either a smaller thrust washer (stainless ring about 7/8" diameter) or as I believe in your case a line cutter, (older type) so if you have all of these fitted then this is not your problem.

No problem - it made me check to make sure I had all the right parts fitted. Thanks.

 

[coliholic]

What you lot need are some spares and it just so happens..................

http://www.ybw.com/forums/showthread.php?t=239779&highlight=volvo+duoprops

Back in Uk tomorrow for the weekend, so could pop them in the post if anyone's interested.

 

[Greg2]

What you lot need are some spares and it just so happens..................

http://www.ybw.com/forums/showthread.php?t=239779&highlight=volvo+duoprops

Back in Uk tomorrow for the weekend, so could pop them in the post if anyone's interested.

I'd have them but they are the wrong size. Mine are B6's.

 

[Kawasaki]

Are you saying it is designed to do this in case of fouling/impact to protect the drive?

In short
Yes!

 

[Kawasaki]

To cut a long story short it turned out that the hub of the rear port prop had separated from the prop


Anyone else experienced this?

Yes, too many times
Whence trying to clear rocks for 'other users' in the Swellies!
I still think this is your prob.
Anyway
Even if it isn't you need a prop/props that don't spin independantly of the shaft!

 

[jparham]

So the cause of no propulsion is indeed the rubber absorber between spline and prop coming adrift.
I have had one 'move' due to running through a load of floating weed and choking the prop and am pretty sure your problem would have been caused by loads of crud on the prop causing heaps of drag when you tried to put it on the plane.
Yes they are supposed to do that to stop the shafts breaking due to too much torque.
So I'd vote for there being nothing wrong, just get a new one/set and put them on (with spacer).
I would also take note that if she's been holed up for a while, run the drives at low speed for a while to clean crud off, then gradually take the speed up.
Could also be caused by aluminium corrosion between prop or splines and rubber shock. nothing you can do about that.