Prop pitch

1988 Ski Natique 351w. Right now the boat top speed is 43. It pulls one skier out of the water just fine. Looking to be able to pull 2 or 3 skiers at once.
I know more torque means less top end. What I don't know is pitch and shaft size.
What pitch prop would give more torque and least amount of top end loss?

Usually, you can remove the "castle nut" and cotter pin on the end of the propeller shaft and look at the numbers stamped on the propeller hub. That will give you a good starting point -- along with knowing which propeller that came with the boat from the factory.

My own rule-of-thumb is that a good all-around prop size will allow the engine to achieve maximum intermittent RPMs at wide-open-throttle (WOT).

Below is the typical information you will need to know when looking at propellers:

1. Engine make/model
2. Name-plate or factory recommended maximum intermittent RPMs
3. Propeller shaft diameter
4. Transmission make/model (direct 1:1 or gear reduction)
5. Engine and transmission rotation

The performance you are getting now will help determine propeller options to consider.

JQ

PROPGUY wrote: ANY SKI NAUTIQUE SHOULD PULL 2-4 SKIERS OUT OF THE WATER ON ANY GIVEN DAY, MY MALIBU PULLS 8. IF YOU RELLY WANT TO CHANGE PROP PITCH OR CUP CALL OJ OR ACME FOR A RECOMENDATION. AS A OJ AND ACME DEALER I CAN RE CUP YOUR CURRENT PROP OR SELL YOU A NEW ONE AT A DISCOUNT.     ROB

Rob,
Thanks so much for your advertisement and advice. I'm so glad you have a Malibu and feel they are superior in pulling over a CC. Also, you don't need to use caps as it indicates shouting.

I've got an '86 with the Acme 540 3-blade prop. This prop would fit your boat, as both have a 1" shaft, the same engine, and the same hull. It tops out at about 37 MPH, but will easily pull 3 or more skiers. My understanding is that the wakeboarders prefer the Acme 542, as they run at slower speeds. I suspect that my boat carries a few extra pounds, since the floor and stringers are original, and the foam is probably saturated. If you've got a dry boat below the floor, you may get more speed out of it. With all of this said, I've never had to get close to 37 MPH with someone behind the boat, but then again, I'm towing guys in their 50's.

That's with electronic ignition, new cap, rotor, wires, plugs, rebuilt carb, and timed at spec. I would generally add an extra 2+ degrees advance, but it ran well enough without it. It tach'd out at 4600 RPM, and for an engine pushing 1000 hrs, I didn't want to rev it higher. I should have mentioned that the top speed was determined with the single "functioning" speedometer. I did not use a GPS to determine actual speed.

There are numerous I-Phone aps for speedometers. Check them against your boat speedo for an accuracy comparison. Like Tim said, yours is probably off by several MPH.