New prop question from a newby

[Quartz]

Wow. What a great forum. I'm glad I found it. I am having a hard time finding an answer to my problem using the search function.

Here's my problem. I'm buying a bowrider with a 4.3 Mercruiser for a family boat. It comes with a 14X23 aluminum prop. I want to put a stainless one on the boat. The dealer is recommending a 14X21 SS prop. He is telling me that the reason for the difference in pitch is that the aluminum flexes and the SS doesn't.

Is he feeding me a line of bull or is this correct?

[Quartz]

27 views and not a single reply?

[Jango]

I think He's stretching the Truth a little. The S.S. Prop is stronger, therefore the blades are thinner, with slightly less drag. All things like weight, HP etc being equal, usually enables slighty more pitch.
If you are intending to pull skiers etc, less pitch is appropriate.

In order to determine correct pitch (without skiers), wide open RPM should be manufacturers max. with lite load - half tank fuel and Driver only. If rpm is too high, increase pitch, rpm low,decrease pitch.

[redtech]

jango is right on about determining correct pitch
best if you can borrow or rent a prop before buying one to see if it's money well spent or just the wrong prop

[Quartz]

I checked with two propeller manufacturers. Both said that if the prop size and pitch is correct with the aluminum prop, I should replace it with the same size and pitch in SS.

I've decided to pick up the boat with the standard aluminum prop. I'll break the engine in and see how it performs. Then I can keep the prop size and pitch when I replace it with the SS prop or make the necessary adjustments.