Which prop for clasic ski boat

Postby oenomaus » Tue Aug 03, 2021 9:48 am

Hi guys, Ive got a 1991 5.4m Supertrac direct drive ski boat (look similar to Lewis Tornado) with a new 350 chevy crate motor. It has 290 hp at 5100 rpm but i never run it past 4500 rpm. It has 326 lb-ft of torque at 3750 rpm. Top speed is 44 mph.
Current prop is an old OJ 3-blade. doesnt seem to have size stamped on it. Seems to perform well, doesnt slip, pulls wakeboarders or 3 people on a tube up to 40 mph easily.
Was interested in a CNC prop to reduced vibrations and to see if it would improve performance.

Any ideas ?

Thanks
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Re: Which prop for clasic ski boat

Postby Feetfirst » Tue Aug 03, 2021 1:25 pm

CNC all the way mate. You’ll never put another hand finished prop on again.
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Re: Which prop for clasic ski boat

Postby feral1 » Tue Aug 03, 2021 1:52 pm

You might find that the numbers are stamped under the nut. Alot of boats that era tended to have a 12x15 (diametre x pitch) 3 blade prop. General rule of thumb is reducing pitch by an inch will increase revs by 200rpm. I have a Skicraft Excel and had a 12x15 3 blade and switched it to a acme 1469 12.5x12.5 4 blade. I still only achieve about 4500 rpm at WOT and about 45 mph, but the holeshot and driving at skiing speeds is much better.
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Re: Which prop for clasic ski boat

Postby oenomaus » Sat Aug 07, 2021 9:41 am

thats good info about the 200 rpm drop.
i had a look at the prop and i cant make out the stamping. what do you guys think?
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