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.