Propeller sizing

[Hoplite808]

I have a 1988 3227 Convertible. Based on the documents I've been able to find it originally came with a pair of Crusader motors with Walter V drives that are geared at 2.05:1. It also has the original 18 X 21 3 blade props. A previous owner repowered it with a pair of Perkins T6.354's and she is at best able to cruise only at about 9-10 knots. I suspect that I need to reprop the boat to match the engines. Does anyone here have any idea where I could find out what type of prop I should have on this setup?

[bud37]

You are going to have to prop your boat based on the Perkins rpm range and the gears that are in the boat now. A good prop shop should be able to help with the decision......there are calculators that can help but there may be some trial and error as you need the engines in their sweet spot at cruise.
What rpm does Perkins say to run that engine package at and what rpm are you at now ? Some other possible questions may be, how heavy is the boat, how big a prop can you get under there safely and what is the shaft size now.....good luck but I think you are correct thinking to change the gears as well if possible.

[bud37]

Any up dates on your prop issues ?