Need to know the engine model and hp, shaft size, transimission model and gear ration and type of prop (2, o r 3 blade fixed, feathering, folding) and max budget for a prop. Alos have your diver check measurment of the clearance between shaft and hull. Then contact a propeller supplier for a quote on one sized for your engine/transmission.
Thanks. Yes I've talked to Beta about the engine, and they offer gear ratio of 2:1, or 2.6:1. Then got quote on Campbell sailor 3-blade prop, which specified either 12" or 14" for those ratios. My issue is I'd like the larger prop, but I think it might be too big. I have one photo of the boat in the sling. It's hard to tell, but looks tight with current prop which I think is 12".. I'm not sure, but 14" sounds big on a 30 footer?
Having someone dive might be the only way to figure it out for sure, but is a hassle/expense I'd like to avoid.
Ultimately going with a 12" like is on now is the safest choice. And considering pretty mild current, tides etc here on the (upper) Chesapeake should be plenty fine. My marina is on a calm river, with an easy entrance, I rarely ever need much thrust (ditto for the areas I go to)