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-   -   Prop for Atomic 4 (http://www.sailnet.com/forums/general-discussion-sailing-related/1269-prop-atomic-4-a.html)

gbeardmore 05-03-2001 01:15 PM

Prop for Atomic 4
 
I have a 1969 Pearson 35 with an Atomic 4 (30hp) direct drive. I am using a 12"x5" three blade prop and can only attain about 1700 RPMs at full throttle (the engine is in good working order). This only generates about 14 hp and gives me very little reserve power. Indigo has come out with a 3-blade 10"x7.4" prop that they claim will give higher RPMs and better performance, with almost no increase in surface area on the prop. Has anyone tried this prop? Any other thoughts would be appreciated!

WesleyBailey 05-08-2001 07:27 PM

Prop for Atomic 4
 
>I am using a 12"x5" three blade prop and can only attain about 1700 RPMs Indigo has come out with a 3-blade 10"x7.4" prop that they claim will give higher RPMs<

As I understand it, the 12X5 prop that you are now using is designed to move thru the water 5" per revolution, whereas a 10X7.4 prop is going to try to go 7.4" each time it screws around. To allow your A4 to rev higher, I''d suggest going to a lower pitch prop, rather than one that is higher.
I have a 30" Pearson with a 12 X 7 prop that only allows me to turn about 1500 rpm. While this is the prop that came on the boat, I have added lots of gear (AC, inverter, etc.) that raised the waterline about 1 1/2". I am also looking to reprop, but I will be looking at going down to a 12X6 or maybe a 12X5. Before I weighed the boat down the 12X7 prop would run her at hull speed, but now I can rarely coax her about 5 knots.

Wes;ey Bailey
P30 Pilgrim


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