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What to do

Sun Tuned

Hi guys,
Been lurking in the back for a couple years now.
I bought a well worn 1989 15’ panther boat. This was to the best of my knowledge used by TVA for Mississippi River bottom use, seismic activity I’m told.

Anyhow it had a 350 with a 2:1 century belt box on it and a 2 blade wood stick. When I bought it it was all there , but, the engine had been sunk and rusted solid. The belt box on the other hand was recently apparently gone through and is still in great shape. The boat hull is still solid but has a few boo boos that are going to need attention.

Sooo… here’s my question. Given the fact I’d like to use this strictly for hunting in shallow shallow river water in some bottomland where the mud is like paste, and sometimes depending on the time of year as much as 10-12 feet deep water in the same places.

If I keep the hull and put it back top notch and don’t wish to change this belt box(2:1 ratio), I still need an engine. I also need a new prop.

I think the prop will end up being whatever I HAVE to choose with the 2:1 ratio. The wild card here is the engine. That is what I do for a living, machine shop building engines. So I can go back with a 350 or a 454/496…

What would you gentlemen suggest I do here if I wanted to keep the current belt drive ratio I have??? And how delusional would I be thinking that this will have a good ending with a boat that works like it should?

Thank you fellas in advance, and sorry for the somewhat noob questions.


Well-known member
If the hull can take the weight build a big inch BBC and put I a 3 blade carbon prop.. The model prop will depend on how much hp you build at 5000rpm. That will be your max engine speed with a 2/1. You can change your top pully in the belt drive to 2.3/1 that would ok with a big inch sbc

Sun Tuned

Thank you!
I know that post sounded kinda vague, and I guess it was really. I know what boat I’m working with, and for now don’t want to change the box , so the engine and prop were the only variables.

The boat hull needs some love. I’ll remove it flip it and get onto that.

The engine choice really isn’t an issue for me as I can choose just about whatever. I as somewhat leaning towards a small block but , in my mind with a 2:1 box to work with I think I’d be better with a bit more torque I think. I could be wrong about that but either way engine and output will not be a problem.

The old 2 blade wood stick had rotted and fallen into the boat when I took delivery of it. So as far as how it works … I’ve no clue. Prop was toast and engine was also. It was pretty much a basket case. But the hull was good. And the cage needs a replacement. Couple areas were split from water freezing in the lower cage posts.

It was close enough for me I went ahead and bought it.

With that said I’ll likely build a 489/496 with some lighter aluminum heads. Won’t get it as light as the sbc, but I think I can get closer than an all iron motor for sure.

600 hp/ 620-630 torque won’t be an issue for me.

That 2:1 box though has me concerned if when I get done, this thing will work like it should. I just don’t want to start out building a turd.

Slidin Gator

Well-known member
That 2:1 box though has me concerned if when I get done, this thing will work like it should. I just don’t want to start out building a turd.
You said you been lurking, so assume you get the speed limit on the prop. More power = bigger prop = lower prop speed limit = more gear or more engine torque.

Aeon is right, 2,500 RPM is about as high as you want to turn a gear drive prop and less is much better. The 2:1 ratio is good for the old SBC 350/350 and is ok for a built BB motor, a 2.3 ratio is way closer to optimum for a built BB motor and the low end of good gearing for a small block that isn't too hot.

If you are set on keeping the box, follow Aeon's lead on the pulley swap for 2.3 on your box and some new belts while you are at it. That hull will work fine for a BB build, definitely spend money on lighter heads and intake. Plan at least 80" prop diameter, 82" possible. You are still looking to make max power by 5,000 RPM with the 2.3 ratio, so go all in on torque.

Sun Tuned

I thank the both of you gentlemen for the rapid replies.

Well for now I’d like to stick with the 2:1 until I get some extra $$$ stashed back and then I can upgrade that box.

I was thinking when I called century back about a year ago that he’d said a 2:3 was the only other option for that box unless I moved up to a ch4.

It’ll come.

Thanks again fellas!


Well-known member
Think it's like 1500 to swap the upper pully, 2.3 is as low as you can go on a ch3.

So build the BBC keep the ch3. Change out the Lower bearing (they are a standard bearing) and put on a new belt.

Here is where it gets interesting, call up sensenich and ask what prop to match up to your motor and box. Make sure it will fit in your cage!!! Wont do you much good if they say a 82"JX would be ideal if you can only fit a 78" prop. Remember tell them the Power at like 4900rpm that's as fast as you can spin the blades with a 2/1 box.

Slidin Gator

Well-known member
Think it's like 1500 to swap the upper pully

That's what we been trying to say, do that!

Wow! Thank you guys.
Much appreciated!
No sense putting money into the wrong prop because you cheaped out on the gearing. 2.0 vs. 2.3 is HUGE. You build a stout BB, put it on a 2.3 gear on the 15 x8 Panther, you good.

if they say a 82"JX would be ideal.

This is what you are aiming at, BB on a 2.3, talk to Sensenich.


Well-known member
Think you'll be very pleased with the BBC/3 bl combination suggested above.
I ran one on my Diamondback for 6 years and could not blow up the 454/375 HP truck engine.

Edit: those are TVA boats in my profile pic here, (at the Chickamauga Dam in Chattanooga TN).

Sun Tuned

Well I sure appreciate the kind info guys!

Looks like I better get to work on this.

I believe I will switch this turkey to a 2.3 and follow the plan.

This is not the first airboat I’ve ridden in. My uncle worked at the nuclear plant outside New Orleans and one of his coworkers let me ride in his when I was like 16. That was the only way you were gonna get to this fellas house…

That was enough. I gotta have one. I’m 50 now. And this is the first one I’ve ever bought.

Not in over my head yet I don’t think. I’ve got the tools and skill set to put this back together. Plus, I bet if I get in a pinch I got you fine folks to get me un lost.

Thanks for the guidance fellas it’s most appreciated.