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gaer ratio

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formula ss

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hi everyone I have a formula 280 ss 06 I have twin 6.2 320hp mpi engines . my outrives both need replacing from salt water corrosion gear ratios are 2.2 to 1 with 28 p props. I have a line on two drives which are 2.0 to1 ratio. and im thinking I will get more speed if I keep the same props. boat is 7300 pounds it has the premium engine option for the boat. runs presently 55 to 58 mph engines seem to have plenty of power for the application. does anyone know if I will get more performance or will this ratio change force me to go down in pitch. or is the ratio change so nominal that my engines can handle the change and maintain the same props to get a bit more speed
 
formula ss said:
4600 t0 5000 full out about 4800,, if I loose rpm from the gear reduction does that mean loss in speed.
thks
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First of all, going from 2.2:1 to 2.0:1 is not a further reduction........ it is a lessor reduction.
Your prop will be spinning closer to engine rpm than it was prior.

If your engine can still pull close to your suggested WOT rpm, you might gain speed.
Hard to say!

.
 
If they bog the motors down, it's easy enough to either remove an inch or so of pitch, or cut a bit off the diameter (or get props with less pitch). My guess is you'll be just fine and get a bit more gas mileage as well. I deliberately over pitched the props on my 32 footer and was pleased with the result. It too was an over powered boat, which didn't struggle in the least getting on plane.

Jeff
 
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