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Repropping 2010 Yamaha EFI F40

gary13

Member
Recommended RPM= 5500-6000
Boat is Carolina Skiff J16
My question is this....why the lack of 'normal' performance gain with the 12-pitch prop below??? All testing was done with boat loaded the same way, close to the same water/wind conditions, with props from the same manufacturer.
This engine came with a 10.25x14 prop that maxed out at 4800rpm, was slow to plane, not much on top end speed, and would not take any additional weight in boat.
Switched to a 10.49x13 which raised rpm's to 5100, better on-plane time and very little increase in top end speed. Any additional weight added to boat slowed everything down.
Went with a 11.6x12 with rpm DROP to 5000 but lowered the on-plane time, top end speed stayed about the same, and allowed for slightly additional weight to be added to the boat.
Last prop tried was a 11.6x11 which would have let the engine hit the rev limiter if I opened it up all the way...I backed off at 6050rpm. Phenomenal hole shot even with 3 people aboard and any change in performance due to added weight was negligable. Top end speed slightly increased.
Has anyone ever seen a prop that was mis-stamped?
TIA for any input.
Gary
 
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