[Public-List] Correction on my Prop Question

[John Birch]

Yup

----- Original Message ----- 
From: "Michael Connolly" <crufone at sbcglobal.net>
To: "Alberg 30 Public List -- open to all" <public-list at lists.alberg30.org>
Sent: Friday, June 13, 2008 9:28 AM
Subject: Re: [Public-List] Correction on my Prop Question


> Richard
>  One thought that I had.  If this is a Diesel then running it at anything 
> over about 1800 RPM is excessive to me. Gas engines normally can cruise in 
> the 2200 RPM range, actually slower is better.  I can get hull speed with 
> my Gray Marine @ 2200 RPM. Prop is two bladed 13 x 9.
>
>  So this Diesel should be turning slower to achieve the same hull speed. 
> I am not a scientist, but it seems to me that turning a prop thru the 
> water at excessive speeds could cause cavitation and vibration?  Can a 
> prop turning too fast rip a hole in the water so-to-speak?
>
>  Michael C
>
> richard.hazlegrove at wachovia.com wrote:
>  Yesterday I asked if anybody could give me some advice for a friend
> regarding prop size on his new Yanmar 3 YM20 which I believe is pretty
> close to the prior model 3GM. I mistakenly indicated a 2.0x transmission
> reduction gear. It is in fact a 2.21x reduction. I also neglected to
> mention that he is looking for advice regarding a three blade prop. The
> engine by the way is rated at 22 hp at 3,600 rpm. Thanks
>
> Richard Hazlegrove
> Quest 433
> Mobjack Bay, VA.
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