Correct prop size and pitch 1984 90 HP Johnson
 

Hello all,
I finally getting very close to Sea trials on my recently acquired 1975 20' SF. I re powered down to a 90 HP 1984 Johnson. The prop is a bit beat up and motor was on a 17' tri-hull before. I know Fr.Frank and Bushwacker both have had experience with this. What recommendation for prop size and pitch ? The options are many in reading what kind of prop CAN be used. I know its a weight RPM issue. Just trying to get a starting point. 31.25 X 15 is what I heard from iBoats.
Thanks Boys.
1975 20'SF
1984 90 Johnson

Re: Correct prop size and pitch 1984 90 HP Johnson
 

The 1975 115 Evinrude I had on my Seafari for 31 years ran fine with a 13.75 dia. x 15" pitch SST prop, with motor raised so cav plate was 1" above bottom. (You'll probably want power trim if you raise it up like that.) That motor was rated at the powerhead, but it was about 90 hp at the prop like your motor, so that size prop should be about right.

Re: Correct prop size and pitch 1984 90 HP Johnso
 

Thanks Bushwacker,
I mis posted 31.25 X 15 I meant 13.25 X 15, I will look at what prop is currently on there and go from there. Thanks again..

Re: Correct prop size and pitch 1984 90 HP Johnso
 

I run a 13x15 on my 19 with a 88spl and it tach's out at 5300.