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I'm gettin ready to buy another airboat soon. The last boat I had was a 12ft by 6 1/2 all 1/8" Ronnies single rear operator, full grass rake, 0290 125hp Lycoming 4cyl and a 5-blade warp drive. This time around I'm lookin for alot more power. I'm lookin to spend under $10K and I see that alot of people over there in Florida, I'm in Louisiana, I see ya'll use those GPUs alot, could someone tell me the basic pros and cons of the motor, weight to hp ratio, how reliable are they, if parts are cheap. Plus I'm also really considering making the transition to automotive this time. I was wondering how the basic 350v8 330hp with a gear-to-gear reduction unit and a wood paddle prop on say a 14ft by 7ft open Hull Ronnies with a full alum grass rake, single rear operator, 1/4" telfon, if that would run dry ground and also run on dry ground to where I could run it up the trailer. And also has anyone ever built a boat with a Vortec V6 with a reduction unit. I'm lookin to run just mainly open marsh,and a good bit of dry ground. Please any input would really help.
As aircraft motors go, I'd say the 220 GPU is the cheapest since there are many of them around. They are also quite reliable from what I've seen and heard.

They are 470 cubic inch and make about 220 HP at 3000 rpm. They're pretty heavy but they will turn a pretty stout prop. My buddy has one on a 12 foot aluminum hull with a 74" prop and it goes like mad with 2 people.

You sound really undecided about what to do. You should really drive some other boats before you spend the money to switch, it probably will cost more than you think
Don't forget about fuel rising fuel costs. I just heard gas is supposed to skyrocket again this summer. You might just be wanting to keep your 290 for a while!
Duckhunter - Have seen several of those 13 & 14 footer with 310 marine 350s in them. They used them in the seismic field and if they didn't go, they didn't get payed. Those guys were given straight lines and had to run them or go home. The old ZZ3s were only making 345hp, so you are not far from those in HP and I know those would push a 14 footer really nice. So I think those 330s would work all right, just cannot turn them up as fast. But with a single seat, you should be fine.

There are some good boat operators and builders around the basin. Ronnie, Mark, and a couple others. Look around and ask questions.

Look through the old posts for something about those LS-1 Vortex (V-6). Waterthunder builds motors and claims to have one that is making better than 350 hp with it. Some of the HP output is almost scarey he gets out of them. He says he will put it on a dynameter for you and show what the HP output is. (Now that is being willing to prove what you talk) With a reduction gear, cooling system, and all needed parts, it is less weight than a Lycoming 0-540 angle valve and putting out more HP. That is a option to think about long term
LS1 is a V8

The Vortec V6 is a different animal and to my knowledge is still in production at least as the base engine in the fullsize GM pickups.

There were early "Vortec" engines that don't have the desirable clinder heads that the later engines have, so beware if you want to go this way.

The "true" Vortec V8 (L31 heads; 255 HP) debuted in the 96 pickups, and if I'm not mistaken the Vortec V6 (4.3 liter) with the good heads came out the year before that.
I'm also thinking about keeping my boat and just bringing it back to Ronnies to get a 180 4cyl Lycoming, I dont want a 6cyl aircraft, I had a 300upstack and it was nothing but trouble, plus I'm not rich like some people and I'm kind of on a limited budget, like I said I'm lookin to spend bewtween 5k and 10k. I have to be able to be able to run on dry ground and run it up on the trailer with just me on it. I mean my 0290 is a nice little sound motor, but 125hp just aint much. Any help is much appreciated people.
O360 sounds like a great idea.

The number of cylinders doesn't have anything to do with reliability though. A GPU seems to be a very reliable unit.

I just think the lighter weight and smaller displacement are a great idea with fuel prices. This from a guy building an SBC boat :oops: The next one will probably be a 10 or 11 foot deck boat with a 4 cyl though