Squeezing a Pint into a Quart Pot

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Old Bumbulum

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I need to replace my Yanmar 3GM with a more powerful unit, so aiming for a Beta 38 as the boat is a Tradewind 35, 10T empty weight.

I know some have done this change before but I can't find the space to fit it all in. (I am asking on the class website.)

The Beta, being a 4 cylinder, is longer than the Yanmar. I have a max from the first transverse frame to the inside face of the deadwood of 105cm. The engine is 89.2cm leaving me with a theoretical space of c.16cm in which to fit a R&D coupling, a shaft coupling and a deep water seal.
The shortest seal I've found, a Radice, is 11.5cm. There ain't much left!

Anyone aware of any really short deep-water seals of any type? I believe the stern-tube is 2 in and the shaft 1 ⅛

Likewise, are there short shaft couplings - or is my instinct that you can't shorten these and expect them to grip correct?

An integrated flex coupling and shaft coupling perhaps?

Any pointers much appreciated.
 
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Had you considered a Volvo D2-40? Also 4 cylinders but I think you'll find it's usefully shorter. It also has a standard 115A alternator.
 
Will you still have enough space around the engine for maintenance? A previous owner of my Furia 332 decided that bigger is better and changed the original 3 cylinder Sole 27HP for a 4 cylinder Sole Mini 34 at 31HP and it's a real pain in the nether regions to get at everything as it's way too big for the engine bay, not only in the length but the width too.
 
colind3782 said:
Will you still have enough space around the engine for maintenance? A previous owner of my Furia 332 decided that bigger is better and changed the original 3 cylinder Sole 27HP for a 4 cylinder Sole Mini 34 at 31HP and it's a real pain in the nether regions to get at everything as it's way too big for the engine bay, not only in the length but the width too.
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I believe the Tradewind 35 has quite reasonable engine access.
 
Yes there are short shaft couplings but probably not clamp types which is possibly better engineering anyway utilising keys and either locating screws and or cotter taper pins through the shoulder (definitely not centre) of shaft and coupling you will find them in R&D catalog
 
We had a similar issue with space for coupling etc when moved from Deepsea seal to larger lip seal and needed shaft space, fitted the bruntons sigma drive and saved about 120mm and quietened the engine loads as well.
 
Thanks guys. I'm struggling to find keyed or splined couplings anywhere though, they all seem to be split clamp-on types but would need to be very short indeed to get inside the Centaflex or Sigma (£ouch!) dimensions with a R & D flex coupling involved as well.
 
Old Bumbulum said:
Thanks guys. I'm struggling to find keyed or splined couplings anywhere though, they all seem to be split clamp-on types but would need to be very short indeed to get inside the Centaflex or Sigma (£ouch!) dimensions with a R & D flex coupling involved as well.
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Maybe I've misunderstood, but why would you want two flexible couplings?
 
If you used the centaflex or sigma you would not need the R&D flex plate, this gives you another 38mm approx, the sigma does not need a key way as it uses a internal taper lock, they do cost but are extremely well engineered, makes a change in the yachting world?
 
pvb said:
Maybe I've misunderstood, but why would you want two flexible couplings?
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Sorry, I didn't make it clear. comparison was intended between centaflex/sigma and conventional clamp + R & D.

The Centerflex certainly looks hopeful but I'm still struggling to find the room for a dripless seal! What I really need is a short-turret greasepacked gland but most are quite long (10 - 12cm)
 
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Do you really need all those HPs?. I know the Tradewind is a heavy boat (I've sailed one quite a bit), but I have a Rustler 36 that was re-engined with a 4cyl 35HP Beta by the previous owner, and I never use anything like full revs/power - the original was a 3cyl Yanmar, which I think is far better suited to the boat.

Otherwise +1 to to the Centeflex, they are compact, and do the job. No need for a separate R&D cooupling.
 
Leighb said:
Sorry, had to say it, but the title seems back to front?!?
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D'uh Oh!
So it is! May I plead insanity?

Do you really need all those HPs?. I know the Tradewind is a heavy boat (I've sailed one quite a bit), but I have a Rustler 36 that was re-engined with a 4cyl 35HP Beta by the previous owner, and I never use anything like full revs/power - the original was a 3cyl Yanmar, which I think is far better suited to the boat.
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Well, a sensible argument, but...your Rustler is a 'mere' 7,5 tons while the Tradewind is 10, and given the traditional 4Bhp per ton guideline that seems way too little. The 3GM was good for my (4 ½ ton) Sadler 32 but certainly not excessive. The 3YM I replaced it with was.

The Yanmar may not be greatly insufficient for the Rustler but I'd venture to suggest that driving a 11.5 ton Tradewind (as it is, fuelled, watered, loaded) the Yannie's mere 24Bhp is quite inadequate as I found on several occasions this summer trying to push into a moderate opposing swell and wind and finding my speed at under 3Kts.
 
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