I have a 9 hp go-devil that currently has a 3 blade prop on it. I want to get a new 2 blade prop. The props listed on go-Devils website for a 9hp is an 8 X 4. I have read before that I should go with a prop from backwater. Backwaters prop for a 9hp is 7x4. So my question is which size should I go with? 7x4 or 8x4

On a side note, should I stick with a 3 blade prop? It seems like no Long Tails are offered with 3 blades anymore. Pros or cons to 3 blade vs 2 blade on a LT.

I'm running a 1648 flat bottom riveted Jon boat. So I am very under powered with the 9hp.

I believe they moved away from the 3 blade for the Go Devil Longtails because they didn't maintain thrust when only partially submerged as well as the 2 bladed props. If you're going to use that undersized motor on that boat, you'd probably be happier with the smaller prop. That boat should have a bigger motor on it, but if you are going to use the 9 horse it would work less poorly with a prop that didn't lug it as much.

I have been researching this a bit. The smaller prop 7x4 will help keep the rpm's up when the motor gets bogged down in vegataion or mud and therefor provide more torqe then the 8x4 with lower rpm's. I also read somewhere that go-Devil 8x4 prop has no cupping where the backwater prop does. And the cupping along with the smaller blade help out when running through vegetation or with a load. But the 7x4 will have a lower top speed then the 8x4.

Does all this sound correct?

I'm unsure about the cupping vs no cupping. Call them both and get their takes on it.

The bigger prop will probably go faster when the boat is empty, but will bug under load. Smaller prop will not be as fast empty, but will less slow under load. At least that's what I've found with my small mud motor.

Cupping may change that.

Sorry to keep this thread going when there's it's twin over there, this is the one I saw first so this is the one I commented on. Hope I'm helping.

Thanks for the input! I'm going to go with a smaller prop, I'm more concerned about performance under load.


I'm not sure why it created a 2nd thread, all I did was edit it my post and it created a 2nd.

I've got a 10hp backwater on a 14x50 sneak boat. Empty I have seen 15 mph. With a couple bags of decoys, gun, bag, etc. it slows way down. I never bothered to GPS, but it won't get on plane and can definitely feel the difference.
I wondered about putting on a 8x4 (currently has the 7x4 that came with it). The prop only has 1 season on it and looks like it did the day I bought it. On my 6.5hp home builds, I always used the 7X5 prop. I still hunt with family and friends running those motors and my 10hp barely keeps me in front of them at WOT.
I was hoping you would go with the 8x4, Quack, so I could hear how it went for you before I tried changing props.