Propeller pitch/diameter question

[boaterholic]

My 420DB has 23x26 wheels. How would rpm change in theory by changing to 24x24, both being four blades?
Thanks

 

[Strecker25]

My 420DB has 23x26 wheels. How would rpm change in theory by changing to 24x24, both being four blades?
Thanks

very roughly, an increase of 400RPM

in my experience diameter is nearly irrelevant in terms of RPM. what ratio transmissions? That makes a big difference in how much of an impact each inch has

 

[dtfeld]

Www.boatdiesel.com has a prop calculator for members. Lots of information on your engines, and worth the price of admission.

There are some free calculators out there as well…

https://vicprop.com/planing_size_new.php/?action=calculate.


You can play around to see what you would get.

 

[dtfeld]

You need to know your current WOT rpm approximate weight and transmission make/model/ratio.

 

[boaterholic]

ZF 280A-1, 1.769:1 ratio for the transmissions.
Current WOT speed is 25.3 knots, RPM’s were 2707/2645.
Couldn’t tell actual weight but would estimate around 32,000lbs.

Thank you for the help