Proper RPMs

[Birdseye]

I have a 1720 cc Key west with a 90 hp Yamaha
approximate weight of the hull is 1,150 lbs
what should my top end RPMS be?

[boats.net]

If it's a 90 2 stroke motor the operating range is 4500-5500 rpm's. If 90 4 stroke, operating range is 5000-6000 rpm's.

[Birdseye]

thanks

it's about 4500+ rpm with a load so I should be ok

[Whitedog]

I have the motor but different boat. This engine makes its power @5000 rpm. I believe you should prop your boat to hit 55-5600 rpm lightly loaded. That way loaded you can remain in the mid to upper rpm range.

[Birdseye]

thanks

[jonp]

Birdseye,

What size prop and brand are you using. I have 90HP 2 stroke on 17 ft whaler. I get 5700 RPMS out if it with a 17 inch pitch stainless. With a 19 it drops to 5000/5100... light load

Jon