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  #1  
Old 10-28-2008, 11:43 AM
Texascoastalfish Texascoastalfish is offline
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Default 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
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  #2  
Old 10-28-2008, 02:33 PM
Bushwacker Bushwacker is offline
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Default 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.
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  #3  
Old 10-28-2008, 03:04 PM
Texascoastalfish Texascoastalfish is offline
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Default 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..
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  #4  
Old 10-30-2008, 11:08 AM
PipeDreamsMarine PipeDreamsMarine is offline
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Default 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.
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Pipe Dreams Marine
"Design her right,
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Bend the throttles,
And let’er eat…."
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