Force 70hp Prop

atengnr

Chief Petty Officer
Joined
Sep 18, 2006
Messages
482
Hello, Ive got this on a 1980 Four Winns 16ft. I dont have a tach yet, but boat runs about 32 mph at WOT. I am running a 11p 11 5/8 dia, came with motor, unclear what boat the motor was on previously; which I suspect is way underpropped. Could someone suggest where I should start on getting the correct prop?
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
16,481
The only way I know is to get a tach.
They sell a Tiny Tach, that, can help.

Or,I think you need a regular Mercury tach, 12pole.

Mercury part#
805289A1 Might work, might not???
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
16,481
Nothing wrong, just the regular tach looks much better on the dash than the TT :)
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
20,614
I wouldn't be surprised if you are pretty close with that prop. Maybe a 13P.
Aim for 5200-5500 rpm with an empty boat, a couple gallons of fuel, and just you in it.

So your four winns weighs 850 to 1300#.......
1980 15' Catalina weighs 825 plus motor and gas
15' Marquise weighs 600 plus motor and gas
and a 17' Marquise weighs 1075 plus motor and gas
There was a 16' Sirocco in 1979, and a 16 Marquise in 1981, which weighed 1000# _ m and gas.

Don't see any 16' 1980 models listed in my catalog.

FYI, that 70 hp Force is using a gearcase originally made for 40 - 60 hp motors.
It uses a small diameter prop with small blades in comparison to similar hp motors from other brands.
 
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