[Public-List] Correction on my Prop Question

[Mike Lehman]

Michael,
 
This engine in this discussionhas a 2:2 reduction gear, so running the engine at 1800 RPM the prop only spins at 900 or less. When I had an Atomic 4 - 1:1 - I would run it at 1400 (engine and prop) to get to hull speed. Not that I have a diesel  (2:1) I run at 2400 RPM (engine) 1300 RPM (prop) to get to hull speed. My engine tops out at 3600 RPM and it was recommended that it should be propped so that you could run it at max RPM - but for normal cruising you should run a diesel at 75-80% of max RPM. At 2400 RPM, I stay a below that, but I am still way up on the power curve and the boat does not slow down through waves, it pushes right through them.Mike Lehman  ><((((º>`·.¸¸.·´¯`·.¸><((((º>`·.¸¸.·´¯`·.¸><((((º>  > Date: Fri, 13 Jun 2008 06:28:21 -0700> From: crufone at sbcglobal.net> To: public-list at lists.alberg30.org> 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. > _______________________________________________> These businesses support your Association:> http://www.alberg30.org/store/A30supporters.html> Please support them.> _______________________________________________> Public-List mailing list> Public-List at lists.alberg30.org> http://lists.alberg30.org/listinfo.cgi/public-list-alberg30.org> > _______________________________________________> These businesses support your Association:> http://www.alberg30.org/store/A30supporters.html> Please support them.> _______________________________________________> Public-List mailing list> Public-List at lists.alberg30.org> http://lists.alberg30.org/listinfo.cgi/public-list-alberg30.org
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