Thanks Skipper It seems that if we are figuring on screwing ourselves through the water (if you will pardon the expression) at 4 knots the propeller should be advancing so as not to "strip the thread" If it were turning a 500 rpm it would turn 500 x 60 = 30000 rev in one hour. Each rev would be 4/30000 nautical miles or 4/30000x6080x12=9.728in This would be the ideal prop pitch. If the prop spins at say 1000 rpm the pitch would be 9.728 x 500/1000=4.864in etc. I found a interesting site on prop design here is the link http://www.boatfix.com/how/props.html Thanks for the information Captain Jim Sadler Skipper sailing vessel Pelican -----Original Message----- From: montgomery_boats-bounces+jimsadler=jascopacific.com@mailman.xmission.com [mailto:montgomery_boats-bounces+jimsadler=jascopacific.com@mailman.xmis sion.com]On Behalf Of Doug Kelch Sent: Thursday, August 30, 2007 6:29 AM To: For and about Montgomery Sailboats Subject: Re: M_Boats: M-15 Prop pitch The Honda 2 hp 4 cycle uses a plastic prop. There was an article in Messing about in boats about how to change the pitch by clamping the tip of the blade, using a heat gun at the base and twisting in the desired direction. The tip clamp can include a longer piece of wood to help set the desired angle. I was going to try it but my local dealer was out of stock on new props and I didn't want to try it on the only one I had. I subsequently lost interest as the Honda works so well as is. I do believe that we could get better performance in waves with a more power oriented prop than comes as standard. Thanks Doug Kelch Gary M Hyde <gmhyde1@mac.com> wrote: M15 theoretical hull speed is 4.8 knots. The Honda 2hp only has one size prop available as far as I know, and it works pretty well on the M15. If you back off the throttle to about 4 knots, you can get ~28 nautical miles per gallon in calm waters. --Gary Hyde 2005 M17 sailboat #637 'Hydeaway 2' We can't change the wind, but we can trim our sails. On Aug 29, 2007, at 12:24 PM, Sandyal55@aol.com wrote:
In a message dated 8/29/2007 11:24:59 AM Mountain Standard Time, jimsadler@jascopacific.com writes:
Thanks for all of the great advise on outboard motors. I have narrowed it down to 4 cycle, long shaft, 2 to 3 HP.
Have any of you skippers used a special prop on the motor? Seems like the prop pitch and diameter needs to match the the shaft RPM, motor power curve and the M-15 haul speed. What is the haul speed of M-15? Since the Pelican is still in keel surgery I have no way to make a speed run.
sincerely Captain Jim Sadler skipper sailing vessel Pelican M-15
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I doubt that prop pitch is very important on such a light boat. Those considerations are more for a heavy displacement yacht.
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