MODIFIED OMC TRIPLE 90 HP WITH TRIM AND TILT 20 INCH SHAFT SHOULD I USE A JACK PLATE OR BOLT DIRECTLY TO HULL /TRANSOM IS FOR A 20 INCH.I'M WARY OF SET BACK AS THE HULL AND MOTOR ARE THE SAME WEIGHT AND THE BOAT WILL BE A HANDFUL TO SAY THE LEAST. ANY INPUT WOULD BE APPRECIATED. THANK YOU/ ROLF.
OMC never made a 90hp 3 cylinder I'll assume you have a 70hp triple that
somebody modified and said it has 90hp. The SST 60 motor was a modified 70
block and it was hard pressed to make 80ish horsepower so you can see why
I even brought it up. Back to your boat. You'll most likely need the
jackplate to get the motor high enough. Use a minimum set back model and
put the propshaft at 2" or so below the pad. If you have the 70hp
gearcase with the .414 ratio try and get a 26 Yamaha drag style prop and
rehub it for the OMC shaft. Rick Krebs won the Nationals in VP75 class
with a combo like yours. That was the prop that worked the best overall.
We tried about everything and settled on that set up. Rick's boat/motor
weighed 845lbs with him in it, and he was 200ish back then. The boat
handled great, even in some pretty bad water. We turned the motor a little
over 6000 rpm then. If you motor is ported then the lack of low end torque
might require a 24 pitch prop for your rig.
Hope this helped.
Please submit whatever questions you have to IHRTechTalk@yahoo.com. All questions and answers selected will be displayed on this page as they come in. Note: though all boaters are welcome, priority may be given to I.H.R. members. Randy can not be held responsible for any advice given. Though his information and expertise is second to none, he has no control over what you do with your boat. It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.
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