Best propellers size -4100 SCB

[shizo]

good morning
any advise on best propellers for Maxum 4100 SCB year of 2000
current propellers 24 Dia.X23 pitch and achieved speed 15 knots and not achieving full RPM.
maybe changed by previous owner.
I'm looking for record of original propellers size with Cummins engines 6BTA5.9-M3.

[shrew]

What is your current RPM? It is my understanding that those engines can be run at Max RPM continuously and can even be propped to exceed max RPM. (Which seems crazy to me).

If you can't reach max rpm, I would reduce the pitch. How many blades?

[shizo]

Hi Shrew,
engine max rpm is 2800
max achieved 2400 or 2450
number of blades are 4