Need Help With Prop Size
 

30FT LONG V BOTTOM TRIPLE STEP NINE INCH NOTCH 4500LBS WITH 675HP AND A SPEEDMASTER #4, RATIO 1.65 X WILL BE EVEN WITH THE BOTTOM.WHAT PROP PITCH WILL BE A GOOD PLACE TO START.3 BLADE OR 4 MY MAGIC 8 BALL KEEPS SAYING TRY ME AGAIN LATER.

z.zuperboat,

I need to know what your WOT rpm will be. If you have dyno sheets on the motors that's the best way to determine that.

With the prop shaft height you mentioned I would go with a 4 or 5 blade prop.

Who makes the hull? Sounds like a SVL boat?

Matt

WOT RPM I WANT TO BE AROUND 6000.THE MOTORS NOT TOGETHER YET THE CAM POWER BAND IS FROM 3200-6800.BUT YES THE DYNO WOULD BE HELP FULL.HP ESTIMATE NOW IS 645-665.BUT THAT MEANS NOTHING WE NEED TORQUE SPECKS. THE HULL IS A SUPERBOAT AND WHEN ORIGINALLY RIGGED WITH 20 GALLONS OF FUEL IT WEIGHTED IN AT 4200.THANKS MATT FOR YOUR TIME.

z.zuperboat,

You should need a 28-30 depending on how the boat performs and what kind of water conditions you plan to run in.

I used 9% as a slip number in these calculations. You should be pretty close to that.

This boat sounds similar to an old A boat.

Matt

I'd email Darin at [email protected] Send in all your specs an I bet he'd give you the answer your looking for .....................:D