Howdy,
I've been lurking for a couple of weeks here trying to learn what I could.
I'm wondering how a "surface drive" prop works. It appears that my homemade 6.5hp prop will not work nearly as close to the surface as the surface drive motors that I see going down the lake. Is it about the prop, or more about the anticavitation plate?
Thanks,
JBJ

True surface drives don't have cavitation plates, a surface drive prop on plane sits half way out of the water and creates more rpms than if it were completely submerged... But if you have a cavitation plate the prop shouldn't be water piercing

Indeed.....
Question---how the heck does the surface drive prop do that without cavitating?
Thanks,
JBJ

Some SD's do have cav. plates, but it doesn't serve the same purpose as a lt cav. plate.

It is there moreless to keep the rooster-tail down and some say it makes it pull harder in the stuff.

A lt prop and sd prop are totally different designs, on a larger hp Lt you can make the prop just barely break surface and gain a mph or two but it you bring it half out it drops in performance drasticly.

I googled surface drive propellers and got some good reading, but didn't fully understand it. It appears the surface drive prop may be a wee bit over my head. After reading about the "local area of nearly infinite pressure" on a normal prop when it cavitates, I'm a little fuzzy on it. I kind of understand the difference between cavitation and ventilation now, but don't see how the surface drive prop is different. I'd like to see a surface drive and normal drive prop side-by-side in person.
Later,
JBJ

The SD prop is wider and has more pitch for example a mb 35 long tail runs an 11 inch wide prop and a 35 sd runs a 12.25 and has more pitch than the long tail

not that it matters, but a 35 lt runs a low pitch 10"
A sd turns a high pitch 12ish"

Alot of that has to do with the gear reduction.

There is a difference between cavitation and aeration. Google those two terms.