I just bought my first surface drive. It's a 2010 Go Devil Surface Drive 27hp Kohler with a 2 blade prop that is pretty beat up. I put it on a 1542 AlumaWeld. The gas tank and battery mounted under the front seat. I'm running am electric fuel pump from the tank to the motor.

I took it out today with my wife and kids. I'm about 265lbs. My wife and kids were on the front seat. Altogether, they're about 250lbs.

I played with the trim a lot, but I'm not sure I ever got it in the sweet spot. I was getting 16mph @wot until I moved my wife to the back of the boat beside me and then I got it up to 19.

Am I delusional in thinking that's about 16mph slow?

I ran a sps long tail with a 22hp Predator last year and I would run 21mph with 2 big guys and a hunting load. Alone, I could get it over 30, but it wasn't fun.

The only thing that's been done to the gdsd is that the guy that had it before me modified an old Honda motorcycle exhaust to fit on it because he wanted it to be quite. I figure the restriction of that exhaust is robbing 1mph or so.

Also, the prop is pretty beat up. So, I'm thinking I can pick up 2mph with a new prop.

So, the questions are

1. Am I crazy in thinking I should be running in the high 20's?

2. Without going into the block, what do I need to do to get some more speed out of this thing?

borrow a prop or get a new one & re-run your test?

What's the bottom of the boat look like? New or old with hooks at the braces?

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21-24 at most with that load on that boat and that motor.

What kind of RPMs are you running? I think the Kohler is rated for around 3600-3700. If your prop is toast you should be getting there at 3/4 throttle.

Move people around to distribute weight differently, get a new prop.


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It doesn't have a tach. I plan to put one on it.

The bottom of the boat has a couple of shallow hooks.

That's about the worst sized boat you could put a surface drive on......short, narrow, with hooks.

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To answer your question about speed expectancy.........

I would think low 20's with a 15' hull not made for a surface drive while being driven by a 150#er.

Asking a 15' boat to run high 20s with a stock 27HP and 515#s in the boat is not going to happen. But you should be able to get into the 20's with a good prop.

I burned up a 2 blade prop on my 35SD and my speed went from 24 down to 18. So who knows how much that prop is slowing you down. Only takes $260 to find out.

One other thing I thought about.
I've got a 22" transom. I looked and go devil makes their boats with an optional "high" transom at 20". Could that extra 2" be hurting me some?

I plan to call go devil Monday and talk to them about it and get a new prop coming.