Identifying a flexible coupling on a Nauticat 331

[Andrew Hollway]

My Nauticat 331 has a flexible coupling between the gearbox and propeller shaft. The engine is a Yanmar 4JH 3TE and the gear box is KM4A. The attached photo shows the coupling. Can anyone identify the make and model? I’ve been given various suggestion, Bullflex or various Vetus ones but they are all subtly different. Thanks. Andrew

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[Paul Jepson]

I believe it is a Vetus Uniflex coupling type 13 or 16.
Paul Jepson

[Andrew Hollway]

Thanks Paul for the suggestions. It looks similar to a type 13 but Vetus indicate this is only suitable for up to 45 HP and the 331 is 75HP. The type 16 appears very different on the vetus website. The whole question arose from a minor vibration in the propeller shaft and the suggestion that the rubber bushes in the coupling might be worn. All the advice I have is that this is unlikely and much more likely to be either a worn cutlass bearing and/or P bracket bearing. The boat comes out of the water next month so we’ll be able to investigate further.
Thanks
Andrew

[Alasdair Woodfield]

Hi Andrew,

I guess you might have discovered the answer by now, here is my suggestion.

I believe this coupling is a Centraflex CF-M as that is what is fitted to my 2006 331.

Alasdair

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[Andrew Hollway]

Hi Alasdair.
I think you’ve hit the bullseye with this suggestion. Looking at the website for Centaflex, it certainly seems the same as mine. Don’t suppose you know if the rubber bushes are prone to wear? I can check it with the manufaturers. I’ve got a slight wobble in the shaft and more shaft noise than I would expect. The various bearing are OK so my last options are, engine mountings wearing or the flexible coupling bushes wearing.
Thanks
Andrew

[Alasdair Woodfield]

Andrew,

No I don’t know much about the bushes, mine seem ok !? I would be interested in any information you can gleen.

One thing that has to be keep an eye on is the earth wire strap acrocc the coupling.

Alasdair

[Andrew Hollway]

Alasdair
I’ll keep you posted. I’ve sent a query to Centaflex and will let you know when they respond.
Andrew

[Andrew Hollway]

Hi Alasdair
Further information on the flexible coupling. You were right, it is a centiflex type CF but there was no problem with the rubber bushes. Turned out that, at some time in the past, it had been taken apart and not reasseembled correctly. Two bolts had worked loose allowing the coupling to patially separate so it was rotating eccentrically. The threads had stripped so we’ve had the whole coupling reassembled with new bolts and torqued to the correct load. The boat is still out of the water so time will tell if it is fixed.
Andrew

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