ASA and PSIA Instructor
Join Date: Apr 2000
Thanked 38 Times in 38 Posts
Rep Power: 18
2 or 3-blade prop?
Sizing a prop to a boat/engine combination is a science, and you would be best served getting the advice of an expert. When we converted our boat to a MaxProp the vendor PYI collected detailed specs on our boat to determine the size and number of blades for the replacement prop. Three was not necessarily simply better. I believe the ability of the prop to transform the engine power into drive is driven by its blade area, you only need three blades when a correctly size two blade won''t fit with the required clearance. As noted previously, too much prop may prevent the engine from operating at cruising speed.
First talk to a pro and see if your current prop is the right size and pitch, if not get a recommendation on what you need - with this size boat and engine, I''d be surprised if a three blade would be useful. Otherwise you may throw money down a hole for no return or worse, buy yourself some trouble.
And I gotta ask, is this a sialboat or a powerboat! Get yourself a folding/feathering prop and enjoy more zip, especially in light air. You''ll get most of the cost back in the value of the boat when you sell it...plus the feathering props like MaxProp are as effective in reverse as in forward.