Need help finding the right size prop

[naturalmystic]

My boat is a 19ft. 1973 Century Arabian V-drive with a Crysler 440 with 330 hp. I will be using it at 6500 ft elevation. Does anyone know what size prop I should be using? With the prop I have now is a 13d-13p and the boat is running with really high rpms (5000 or so) and not really planing out very fast. I would like to use it for water skiing. Thanks

[Jango]

What RPM do you want to run at? Weight of Boat with half tank of fuel and Driver? Also V-Drive Ratio - 1:1 ?

[marshmat]

Hi naturalmystic,
Without knowing the hull configuration, weight, torque curve, etc it's hard to specify an ideal prop from scratch.
But you can look at it from the perspective of "here's what I have, I want to change it a little bit from that and see if that's better". Looking at it this way: You have a 13x13 prop, you're revving a bit high, and you want better low-end bite for fast planing and water-skiing pull. That implies you need more thrust at the lower RPMs, and you can swing a slightly bigger prop at the top end. If low-end performance were OK in the present state I'd suggest going up an inch in pitch, but since you want better low-end bite, I'd suggest you add that inch to the diameter instead. Try asking your prop shop what they think of testing a 14x13 on it, if you have the clearance for a prop that size to not hit the hull.
Another factor - what style of blades is the current prop swinging? Sometimes a different blade shape can change the way the boat behaves.