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thinking : how much Hp wold this need

goldhunter_2

goldhunter_2

Well-known member
I was wondering if there is any formula to figure how much minimum HP is required to push a boat dry without problems?

My current thoughts :

welded 3/4 deck over Hull, cage, stands, rake........ 723 pounds
(doesn't include people,load or engine)

poly weight unknown (7'x 16')

How much engine would this require on the minimum , any ideas :?:
 
There is no mathematical formula that I'm aware of. Keep the weight down. Some of it depends on the style hull too. Some hulls just run the hill better than others. A lot of it is technique.

Do you want aircraft or car motor??

Is your hull 16ft?? You say you have a 7'x16' piece of polymer.

Adam
 
Then there is running the hill and there is
RUNNING THE HILL.
You can run dry in general with X HP. or you can run dry and climb mountains with XX HP.
Tim
 
blackpowderscout,
The hull I sketched out would be 16' long (plus 4" rake) and the flat bottom would be 7' wide with two chines and a riser making the top deck 8' wide. I could build it lighter but have added extra weight in the figure for a .125 sheet and ten stringers centered every 8.4 inches to handle any abuse I may inflict on it :D

My air boat now has a 4 cyl cont with 470 jugs putting 180hp and I would like to stay with a AC motor but not sure I could buy one right off :? so am wondering if this will work for now. my other choice is a SBC400 witch I have in the other boat if I sell with out the engine but then I add alot of weight and have the added cost of a gear box plus have to mess with a radiator , but that is my back up idea

bravo1218,
ok well I want the alum for lighter weight and take more beating . I want to climb over the dikes and marsh, fields ect with out having to worry about calling someone to come get me, basically all the stuff I am worried about doing with my current boat. it does not have to be a race across the hill just as long as it gets there with out any trouble
 
goldhunter_2":1ue7nsa4 said:
My air boat now has a 4 cyl cont with 470 jugs putting 180hp and I would like to stay with a AC motor but not sure I could buy one right off :? so am wondering if this will work for now.
Click to expand...

I would say...NO. I personally don't see a 4cyl w/470 jugs pushing a 16ft boat with polymer on the hill very well at all let alone climb dikes and what-not. If you can't afford at least a 300hp aircraft motor for that setup I'd say go with the car motor and save up for the reduction unit and a good prop.

Adam
 
gh2, why such a big boat? I think you would have to put alot of money into a motor to run well on the hill in a 16x8 ft boat. A friend of mine has a 15x8 ft boat with an 0540 (260 hp) on it with a 2 blade sensenich. It does not run dry very well. Great motor and prop. Just a big boat.
 
blackpowderscout":2xjrdd7n said:
goldhunter_2":2xjrdd7n said:
My air boat now has a 4 cyl cont with 470 jugs putting 180hp and I would like to stay with a AC motor but not sure I could buy one right off :? so am wondering if this will work for now.
Click to expand...

I would say...NO. I personally don't see a 4cyl w/470 jugs pushing a 16ft boat with polymer on the hill very well at all let alone climb dikes and what-not. If you can't afford at least a 300hp aircraft motor for that setup I'd say go with the car motor and save up for the reduction unit and a good prop.

Adam
Click to expand...

Blackpowderscout,
thanks that is kinda what I am trying to figure out I may just have to wait until I can do all three at the same time (Prop, AC engine and build hull)


John C,
why so big ? well mine now is only 12' and fells cramped an no room to carry stuff if I wanted to. maybe it's to big but what I want :D

Your buddies boat sound like a good comparison I have a few questions hope thats ok.
1) my hulls rake will start after 11.5 feet form the transom , Where does his start?
2) Is his hull a true flat bottom or rounded?
3) any idea what his hull and rigging weight is so I could compare?
4) Bottom surface area (area that contact ground) does he have 7 or 8 foot wide?
5) what do you mean does not run the hill real well, can he get over the dike or can't?
6) would his boat do better with a three or four blade prop?
 
gh2, he has the same hull that I do. 15x8 ft Apache. I live in palm city, not far from you. pm me if you would like to take some measurements. I dont think he could make it over a dike loaded. I think he has the prop that he needs for the 260 HP 0540. the 300 HP 0540 runs good with the 3 blade. I like the 15x8 ft hull, lots of extra room. We duck hunt on lake O. Carry lots of decoys, 3 or 4 hunters with gear,cooler, and sometimes a dog or 2. The problem with big boats is that you tend to fill them up with alot of stuff. You need to set the boat up with enough power to push a full load dry, and up a hill or over a dike. Nobody likes to get out and push a big heavy boat.
 
Just a thought, there's pretty big difference from 12' to 14' to 16'. Put a 12 foot boat next to a 16...BIG difference

Try to run a few boats larger than yours to see how they feel before building a hull. You might decide a 14' will be big enough and that will save a lot of $

Or you might still want a 16', but hey, you won't be out anything.
 
I'm pretty sure he meant 2 pounds to 1hp. Good luck affording a 1600Hp motor for your 800lb boat :p

You'd probably want a 400hp or so if you use his figure.

Faron (airboatcapt2) has built a bunch of big boats that perform pretty good. Maybe he can chime in here with some insight.

Adam
 
I have around a 600HP motor with a 1300 pound boat! It's around 2 pounds per HP. Personally I can't afford anything more or I would build it!
 
thanks for the in site so about 361 hp or maybe 400 to be safe. I am going to have the same afford it problem when it comes to engine and prop if I try to do it all at once. I guess this is why careful planing is important :in site:
 
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