Original Prop Specs

  • northstar56
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11 years 2 days ago #263 by northstar56
Original Prop Specs was created by northstar56
We've just bought a 1987 Brewer 12.8 Cutter K/CB with a Perkins 4-236 85 hp. The current prop has some electrolysis damage due to faulty shore power. Photos show plating oxydization. We'll send it to Max Prop but if it's too far gone to repair, we'll be buying a new prop. Would you be able to help us with finding out what the original prop was for our boat?
Thanks,
Karen

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  • northstar56
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11 years 8 hours ago #267 by northstar56
Replied by northstar56 on topic Re:Original Prop Specs
Is there another place in discussions I should have posted this question?
Thanks
Karen

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10 years 11 months ago #268 by Gerry O'Donoghue
Replied by Gerry O'Donoghue on topic Re:Original Prop Specs
Hi Karen

Sorry for the delay, this forum is only recently getting up to speed.

From a previous survey the propeller on my boat, a Whitby 42 - 1977 vintage, with a Perkins 4-236M, 85HP was a Michigan "Dynajet" 18" X 11".

Sorry to hear about the demise of your Max Prop. One of those is on my wish wish assuming I have any money left over.

Regards

Gerry

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10 years 11 months ago #270 by Dan Pedersen
Replied by Dan Pedersen on topic Re:Original Prop Specs
Some more outdated info, I have 1975 Whitby 42 with the 80 hp. Ford Lehman, my prop is an 18 x 12. Not sure if that helps but more info can only cause confussion....

As for the Maxprop, does anyone have any first hand experience with it on the Whitby? Does it add any speed? Does it allow any better control in reverse? I would love to get better performance in both of these areas, but it is a lot of money to risk if the inprovements are negligable.

Dan

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  • gltemple
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10 years 11 months ago #271 by gltemple
Replied by gltemple on topic '84 Whitby 42
My destiny is an '84 bow-sprit Perkins 4-236 powered Whitby 42. The fixed blade prop I removed was an 18 x 12....RIGHT HAND prop. My understanding is that Lehmans are left hand props. Almost all references will refer to a Whitby 42 prop as a left hand item. It's important to note the distinction if you are going to replace the prop. Fortunately a Max Prop can be configured as either, however it's much easier to get it correct the first time.

I configured our max prop to a 12" pitch. With the Perkins we are able to run up to max recommended rpm, however we "cruise" at about 1500 rpm. As I'm writing this, I remember that our transmission was replaced a couple of years before I bought our boat. I wonder if we have a "stock" ratio! Papers are on board and not at hand. I've learned there is no such thing as a "standard" Whitby or Brewer.

When reproped with a Max Prop I didn't think there is a noticiable difference in forward speed, however a precise before and after measurement was not made. There is a world of difference compared to a fixed prop in reverse. We are able to generate flow over the rudder much more quickly. It makes quite a difference when your prop can change to operate in forward or reverse correctly.

Installation of the max prop was straight forward. The prop shaft had to be shortened a bit but the prop aperture did not have to be altered. But, as with all things Whitby / Brewer, some owners have had to alter the aperture.

The real benefit of a max prop is sailing. A fixed blade prop can slow the boat down by as much as a knot.

P.S. I am going to move this thread to Diesel Propulsion.

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10 years 11 months ago #273 by Dan Pedersen
Replied by Dan Pedersen on topic Re:Original Prop Specs
Thanks Greg,

To clarify, I was thinking about under sail when I was interested in increased speed. I guess this will not change hull speed (I have hit 8.5 knots) but will lower the wind speed to get there. Or more precisely, improve performance of the boat at lower wind speeds.

Dan - Akupara

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  • northstar56
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10 years 11 months ago #274 by northstar56
Replied by northstar56 on topic Re:Original Prop Specs
Thanks for the feedback. Lots to consider. I contacted Ted Brewer by e-mail and to my pleasant surprise got a reply today. Possibly because he's a fellow Canuck?
Apparently, our Brewer 12.8 was designed for a 40hp engine so the answer is not straightforward. Using the gear ratio he's doing some calculations taking into consideration our 85hp engine and will advise as to the correct replacement prop.
The Max Prop isn't out of the picture yet. Max Prop has advised they can usually repair pitted props for a ball park cost of $300-$800. We'll send it to them for an assessment. Given the possibility of an extra knot under sail, I"m all for keeping the Max Prop if at all possible!
Karen

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