What knowledge is out there on which make of folding/feathering prop is optimum for a Parker 27 with standard Yanmar engine.
Also how much does it improve boat speed when sailing?
It's a big investment so I would like as much advice as possible.
Cheers
Steve P27

With regard to the speed advantage of folding props the manufacturers have wild claims. One suggests 'up to' 1 knot in 5 ..... a 20% advantage which is ludicrous.

The Portsmouth Yardstick (despite the fact that it is not the best handicapping system in the world but at least based on results rather than theory) has a correction of 1% from folding to fixed 2 bladed prop and 3% from folding to fixed 3 bladed prop.
The apparent discrepancy between the two is based on the fact that the racing guys usually rotate the shaft to 'hide' one of the blades of the fixed two bladed prop behind the skeg while racing.
Chris. Elsa. SS 103

Thanks for info -- 1% seems almost negligible if I can "hide" one of the blades -- hardly worth the £600 expense. Any other views out there?
Cheers
Steve P27 Red Storm

Steve,

As with all things it depends where your priorities are, and what you are hoping to achieve. My SS26 Evangeline has a 2 blade Gori folding prop which came with the boat. Gori are generally considered to be among the best, and it certainly is very good, but at a price. If you are less bothered about performance then the added cost of 2 blade folding over 2 blade fixed may not be worth it. In my experience there's not much difference in performance (power and manoeuvrability) between a two blade fixed and a two blade folding. However, a 3 blade prop will give you much more "grunt" to push through a choppy sea, and better manoeuvrability, especially going astern.

In calm water I can get 6.8 knots flat out (Beta 13.5hp) but a short chop will take 1.5-2 knots off this. A 3 blade prop will give more push to maintain boat speed in lumpy conditions.

I also think 3 bladed props suffer less from prop walk, which is again an added bonus for general manoeuvring under power. Obviously the trade off with three blades is the significant increased drag.

The Gori on Evangeline has very little prop walk, but one of the members at my sailing club used to have a lift keel Evolution 26 with a somewhat cheaper 2 blade folding prop that had so much prop walk it was pretty much impossible to go backwards in any sort of restricted space. As already mentioned the Gori props are expensive, but if you do go for a folding prop I would certainly recommend them.



John Guess
SS26 Evangeline

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Hello Steve, I replaced the original folding prop (1997) with a 2 blade feathering prop in 2005 on my Parker 275/58 "Abacus". Yanmar 1 GM. I was thinking of changing to a fixed prop to improve performance in choppy seas (and keep up with the the rest of the fleet on Seal cruises)but was persauded by Chris Hares of Darglow to go for the maxi prop feather. Compared with the folder the feather is much better in choppy seas and reverse is a transformation for backwards motoring and stopping! I am pleased with it.

Suggest you have a chat with Chris Hares- 01929 556512. website "www.darglow.co.uk". Serious racers usually have the folding prop but for the cruiser/occasional racer I think fixed or feather is better.

Parker 27 Sea-Ell also fitted one of these and my friemd with a P325 had the 3 blade version which took us from the south of France to Turkey this April mostly under motor.

Clifford Miller

I have a 1995 Parker 275 with a Yanmar 10hp engine. I propose to fit a Flexifold 14x9R folding propeller to the boat as I have used this type of propeller successfully on other boats.

My problem is that I cannot measure the existing shaft size accurately enough.

Can anyone tell me if the shaft is an imperial IMP 1” dia shaft with 1:12 taper or a metric ISO 25mm dia shaft with 1:10 taper.

Has anybody worked this out before when fitting a new propeller?

Hello Andrew, the invoice for my 2 bladed classic Maxi Prop fitted to my 1997 build Parker 275/58 shows metric. Details as follows.
" 25mm, 1:10, 60mm hub length,6mm key, 5/8 in BSF nut. Recomended pitch setting=18 degrees Right Handed"

Additionally "14 inch diameter 2 bladed, for !gm engine and 2.62:1 gear box ratio. Bored as pattern supplied"

Hope this helps.
Clifford Miller