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Old 04 July 2016, 03:16   #11
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,618
Originally Posted by Pikey Dave View Post
Are you sure about that? Normally you gain rpm when changing from ally to stainless for the same pitch.
Backwards. SS is stiffer, so it holds pitch under load. Aluminum sheds a bit under load, so revs higher. In addition, SS props usually have more cup, and weigh more, both of which lower rpm even more.


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Old 04 July 2016, 06:50   #12
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 3,995
is is actually a 90 as its not just swapping the carbs.. my SR 54 ran 13x19 and would gain just touching 40 at 5300..(documented figures at the time)

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Old 04 July 2016, 07:43   #13
Country: UK - Scotland
Town: Denny
Boat name: Hebridean Storm
Make: Coastline
Length: 6m +
Engine: Honda 130hp
MMSI: 235107505
Join Date: Mar 2013
Posts: 499
400-500rpm would be a lot on a like for like. I've found very little change in rpm and maybe a couple of MPH improvement at the top end. The blades don't flex as much but they're thinner and present less rotational resistance.

I did find the slip from a vented Laser 11 let me push the pitch a bit further without compromising hole shot. (compared with the Vengence I took off).

40mph+ with a 15" would have to have a unusual gear ratio at 5500.

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