Prop Shaft Coupling

[xstucker]

I have a 1.25 inch prop shaft which is connected to my Yanmar 3GM30 gearbox by a coupling which I have seen on many boats I have sailed, but I don't know what manufacturer it is from. The problem I have is that there are some little lugs that go through the coupling and into some dished parts of the shaft. This is instead of a keyway, but the lugs have become worn at the shaft and thus the coupling spins when in gear, but the shaft doesn't. I have tried to tighten the lugs, with some success, but I suspect that they have a domed end that is worn. Any advice on names of shaft coupling manufacturers would be very gratefully received, so that I can find out where to get some replacement lugs.

Thanks,

 

[sailorman]

photo ???

 

[neil_s]

When you talk of 'lugs', do you mean Allen grub screws? It is very poor practice, but these are sometimes used instead of a proper key. They should have a taper point which fits into a 'dimple' drilled into the shaft. You might find that no dimples were drilled into your shaft either! If you unscrew the grub screws completely, you might be able to see if dimples are there and if not you could drill them yourself. You could also replace the grub screws with hex head bolts (with a taper point filed on the end) which could be nipped up a lot tighter - keep the bolts as short as possible to reduce the risk of them catching any loose material when they are spinning round, though! Another possible in-situ solution is to cross-drill the shaft coupling and shaft and fit a bolt through the whole lot. Use a high tensile bolt and make sure it is well fitted, though.

Best of luck! Neil

 

[Tranona]

The normal Yanmar half coupling is a clamp fit with no keyway or grub screws, so difficult to comment without seeing what you have fitted.

 

[rudolph_hart]

My current, and previous two boats, has Yanmar (3GM30F, 2GM20,3GM30) and all had a flexible shaft coupling made by Centraflex. Is this what you have?