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On my 1972 b31 I'm running 4 bladed bronze 20x23 HyTorg wheels with a lite cup. they are getting thin. I have the opportunity to pick up a set of new 4 bladed NiBrAl Michigan 20x24 DQX wheels with a #6 cup. With the old wheels I cruse at 30mph loaded at 2400 rpm. The boat is a fbc with cummins 6bta 250hp engines, the gear ratio is 1.532.one other thing the boat handles very well around the dock. My questions are if I run the new props as is, what will be the over all effect as compared to the old props and would a good prop be able to change a #6 cup to a light cup if that becomes necessary.

thanks in advance for any and all help...Russ

Russ

I have the 270 Cummins running 21 X 23 and I believe about a 3 cup. Also using DQX. I am betyween 24 and 25 knots at 2400 rpm's. I do not have a tower or Hard top so I am running light very little wind drag.

If I drop my Bimini, I gain a knot.

You should be good, the extra cup might keep the RPMs under thee 2600 RPM load but you will not know until you give it a try.

thanks Tony I checked with a prop shop , no problem changing the pitch and cup...Russ

Russ, sounds like another study in "metallurgy"? Good luck.

Russ Pagels wrote:thanks Tony I checked with a prop shop , no problem changing the pitch and cup...Russ

Russ

First time out of the box, we pretty much hit the nail right on the head. I hit 2650 RPMS on the first go and 23 knots at 2400 RPM's. We re-conditioned the props the third year and tweeked the cup a little and got her up to 24 knots at 2400 and still had 2650 on the top RPM's.