Prop size fo a Cal 39

[John Cookson]

I have had a 3 blade propeller on by Cal 39 for many years (25). The boat has never reached haul speed under power. It has the standard Perkins 4108. I can only get up to 5 knots with a clean haul when I should be above 6. I must have the wrong prop size. Does and one know the proper size 3 blade that should be on the Cal 39.

 

[Tim]

Depends on Engine

I just installed a new diesel in my boat and had to get a new 3 blade. In choosing the blade it had little to do with the boat and almost everything to do with the engine. The only thing on the boat that mattered was prop shaft diameter and clearance from shaft to hull.Call a prop dealer and they will ask for RPM, gearing ratio etc and plug it into a program which will give the best size and pitch. This combined with the shaft diameter and clearance should tell you what you need. I used Tacoma Propeller, got exactly what I needed.My guess, and I am no expert, is with this if you can't get hull speed it may be the engine.