Yacht Propeller – Need a recommendation for getting one designed/made

[BobnLesley]

I don’t know much about them, other than they’re great for coiling up loose ropes, but we think we need a new one: Our yacht (35 foot long keeler) was re-engined a couple of years ago and we suspect that perhaps the existing 3-blade propeller wasn’t changed?
We quickly noticed that the engine didn’t/couldn’t achieve the manufacturers recommended cruising/maximum rpm, but to be honest we didn’t see that to be a problem: Lower revs but still able to reach a decent speed and presumably with less fuel used? However, we’re now discovering what seems to be a problem with cavitation and that we’re not happy to live with: In flat water it’s not really an issue, though even then we do hear the occasional ‘gurgle’ from the area of the propeller, but any sort of head-seas immediately highlight our problem: If the boat’s speed gets ‘checked’ by a wave, the propeller then seems to struggle to get a ‘bite’ on the water, there’s lots of gurgling and it seems to take an age for the boat’s speed to begin returning; if the seas are short, this delay means that the next wave often hits whilst speed’s still down and the problem is exacerbated.
So any opinions on where to look for a new one? I would note that whilst the modern folding and feathering props sound very impressive, we’re planning to head off the beaten track and don’t want to fit something that may later give us a maintenance/repair issue away from the main yachting centres, so unless they're self-fixable (somebody said the 'kiwi' prop was?) we'll have to give them a miss.

As ever any & all comments & suggestions would be appreciated.

Bob

 

[JimC]

http://www.crowthermarine.co.uk/ Not used them myself but a number of people I know have been highly satisfied with them. They design & manufacture all in-house. Being up north and not exclusively yachty they are likely to be better value than some alternatives.

 

[RobBrown]

I got a lot of helpful advice from First Marine in Soton when I was looking at possibility of putting in a replacement engine and so working out whether needed new propshaft/prop etc. Very knowledgable. All this on the phone without charge and in the end I went with reconditioning the exisiting donk, so I didn't give them any business, but can at least give them this favourable mention!

http://www.1stmarine.com/

 

[Tranona]

First thing to do is to feed your boat's data into the Propcalc programme on www.castlemarine.co.uk This usually give a reliable indication of the most appropriate prop size so that you can determine whether the one you have is anywhere near right. Typically when boats are re- engined the prop must be changed for two reasons - first the direction of rotation and secondly the shaft speed is usually different because modern engines usually rev higher than old engines, although the gearbox ratio can compensate for some of the difference.

When you have your ball park figure you can go to a supplier such as Sillette Sonic or T Norris and give them the same data and they will make a recommendation. It is unlikely you will need anything "special" but you may have a choice of types. Best to take the recommendation of your chosen supplier as you will have some comeback if they get it wrong.

If you want to go further and have a folding or more likely a feathering prop then there is a wide range of suppliers, but be prepared to spend at least 3 times, but more likely up to 5 times the price of a fixed prop.

 

[G12]

Teignbridge propellers
Bruntons Propellers
Darglow

All have excellent reputations.

 

[pappaecho]

I replaced a Perkins 4108, with a Beta 35. The engine was held back by the prop and the boat did 3.5 knots on tickover.
Used a free software programme called Propcalc, which indicated a prop of 15 x12, rather than the 15 x15 fitted.
Ordered same from a local supplier in Southampton, and now revs to maximum engine speed and does 1.5 knots on tickover

 

[GrahamM376]

http://www.crowthermarine.co.uk/ Not used them myself but a number of people I know have been highly satisfied with them. They design & manufacture all in-house. Being up north and not exclusively yachty they are likely to be better value than some alternatives.

+1

I've used them several times and always had good service.