20hp + stainless solas?

[Tim Kelly]

I have a great little aluminium 12ft mini bass boat I built from a hull. I run a 9 pitch aluminium on it when there are two of us in the boat, but sometimes a 10p on my own as it hits the rev limiter solo with the 9p. I bought a solas 9p stainless for it and it seemed to have much more lift and smoothness, but it cavitates when I get on plane. The cavitation plate is level with the hull, so the prop isn't super high, but it seems like it's sucking air. No real option to drop the motor any deeper as I built the transom up to the perfect height for the aluminium props. Just wondering if anyone else had experienced this? I tried an aluminium 4 blade solas a couple of years ago and that would cavitate at about 5mph!
finished boat.jpg

[billnorman1]

Cute boat, and your river looks like it has plenty of shallow spots.
I guess that is a Suzuki 20 hanging off the back. Is it a 4 stroke?
That's a semi-vee hull, right? I had a 16 foot semi with a 65 Suzuki 2 stroke back in the day, it would really fly, just wouldn't turn at speed.
It sounds TO ME like your motor is set too high, but you gotta live with what you have.
I suggest you buy a whale tail, because it sounds like you're sucking air into the prop. They are relatively inexpensive OR you could make your own.
Yeah,I know it sounds like I'm whale tail happy but they have worked for me.

[Tim Kelly]

Funnily enough, I have one fitted already. I think it's probably too high as well, though I'm a bit surprised that a ss prop would need to be run deeper than an tin one, though iff the SS has more lift I suppose it makes sense. The boat is flat at the transom with a shallow V at the front

[Pulsare2020]

Funnily enough, I have one fitted already. I think it's probably too high as well, though I'm a bit surprised that a ss prop would need to be run deeper than an tin one, though iff the SS has more lift I suppose it makes sense. The boat is flat at the transom with a shallow V at the front

The additional lift could be a factor like you mentioned. Was there a difference in the diameters of the aluminum and stainless prop in addition to the extra lift you are seeing. If the prop slips more perhaps you could get some additional cup put into it?

[Tim Kelly]

Thanks. It's a bit of a shame as the SS prop has some obvious cup on it and seems to be a lot smoother at sub planing speeds, but never mind, the Ali prop works fine, I was just surprised that it would need to be run deeper than the cheap tin prop. Live and learn. I guess the transom height I ended up with for the tin prop was a much finer calculation than I realised.

[billnorman1]

Break out the recip saw.

[Tim Kelly]

Tempted