new guy with out a clue PLEASE HELP

[Coyotes-R-Us]

NUTTER new guy with out a clue.
A few years ago my boy (42 ) and I built a 16' mud boat for hunting and fishing. It has a 35 hp. Koler Mud devil long tail on a 16.5 Aluminum john boat . WORKS FANTASTIC!
NOW we want an airboat. We recently got a 1600 cc VW bug motor should be about 50/60 hp. and are looking for a 14' Al hull. I think we want to keep the center of gravity way low so we are thinking 'bout keeping the seating in side the hull, and the motor on the floor . What do we need to be looking for in a hull, Different then a flat john ? What kind/ size of prop do you think we will need ?
We don't have a lot of weeds to push through but will have to drive the boat across some flats with out water 20 /30 yards. We want to use it on the ICE when the rivers mostly freeze, It'll open a LOT of hunting land other wise non accessible.
Hope to carry 3 people and 30 goose decoys, guns and ammo .
HELP PLEASE thanks

[Flathead]

CRus, I see you have a pretty good idea of what you want your boat to do! That's a great start. Surf around the site a bit, there's lots of good information in here! Guys who have tried something similar to what you want to do. I had some experience with using a VW motor, Check it out under "Flathead's Combee Tomcat" in Other Builds. I eventually gave up on it in favor of a 582 rotax motor.... Flathead

[Corky]

Hello and welcome to the site !!
VW engines are a popular choice there's quite a few being used in this area...Design your boat carefully...A low center of gravity is a good thing but keep in mind if you somehow spring a leak you'll have trouble in an instant with the engine being too close to the floor...I've seen boats designed with the engine down low and a belt drive to get the prop to the correct height and it seems like a good idea...Find a happy medium with the engine height...Stripped down VW engines are'nt all that heavy to begin with...The only problem I've seen would be the cylinder head temps creeping up if you run them hard for long periods depending on the prop being used...And with the engine installed low in the hull you'll need to address the air flow needed to keep your engine happy...

[Coyotes-R-Us]

Cool thanks.
I'm definitely going to use some of the ideas .
Please continue

[Coyotes-R-Us]

Now.
This has to happen on VERY limited budget. We "fund" our little projects on the $$ we get from harvesting furs mostly coyotes .
In the past we have bought a used snowmobile, a used jet ski, and the mud boat, the largest cost of all.
All we have is a used VW motor that "Should" run and an idea. At our altitude (4000'+) at best the poor old bug motor will probably by a 45/50 hp.
IF you where to guess How big a prop will it really turn? Two , three Blade wood composite? Pitch? We only have one chance on this at the $$$ of props and all.
In reality What size hull? It has to be Aluminum. Two people and some hunting gear.
Thanks
CRU

[sreedy]

I have a 1800 cc vw on an aircat 11' fiberglass. With a 52" arrow prop I could almost plain out in deep water. I could only do 5 mph with 2 adults and a kid on board. I am currently working on a prop. If all goes well I will port some pictures after I do some testing.

[Coyotes-R-Us]

Man I'm back on track with this thing I'm calling the water bug.
Still no hull or prop but a step closer.
I'll get some pictures up later.
My Fabricator FINALY called me and said " your flywheel drive is finished. You want to come and get it ?" Man are you kidding , it's been over 2 months and most the work has stopped till I get the drive on and can get some measurements. I replied Very calmly sure I'll swing down and pick it up. With out even tying my shoes I grabbed the closest jacket and was at his shop in a little over 5 minutes.
Remember the first shop I took it to wanted $500 and the next one said Lets start at a grand and see where it goes from there!!! I gather up the motor, and the new drive and asked over my shoulder, well How much ?
He kinda grimaced and said what do you think of $220, I had around 2 1/2 hours in it . I had my Visa out and in his hand before he finished the sentences...

While I was with out a drive I did get a Tack, oil presser, and head temp gauges and had them all hooked up.
Changed the oil and screen, flywheel seal, and exhaust manifold gaskets changed. I also put hooks on all corners of the motor to lift it with a winch.

I have been in contact with the prop people too.
There recommending a 62" two blade, prop.
The pitch depends on the rpm witch I did not know till I get the drive on and running and they will match it to what ever hub I come up with.$450 and $35 freight.
Hub I'm going to with a Mustang front spindle and hub, old one before FWD and Disk brakes.

I'm going to make the entire motor/drive/prop/seats, and all the controls in one Modular. That way I can set it on ANY hull. We will start with the boy's mud boat hull and see what we want.

I still can see a catamaran hull and that th way I'm planning on going

[Rollbar]

Pictures of the work done. Awesome score on the flywheel drive etc. Sounds like fun.

[WBS]

if you are considering a catamaran hull you should read up a bit on Sea-Sleds. There is a design by Bateau boats called a Texas 18 for use in shallow to deeper water. The front end is an upside down V that gets air under the hull and breaks the water impact. You could flatten the design and shape the back half like a essentially flat airboat hull. if you don't plan to go in high weeds and debris-filled air you could consider a propeller shroud like the hovercraft guys use for high thrust with smaller diameter props or fans. Those guys use low-mounted engines with belt drives for a low c.g. Propeller shrouds for thrust use are not cages. they are a like a plane wing curved around into a close fitting ring around the prop and made of fiberglass or other composite. They can double the thrust for a given prop diameter and hp. They have to be done right but certainly aren't beyond the skills of the guys I see commenting on these forums. It sounds like for the power you are considering a 4' to 5' diameter one would be about 2' long and 3" deep would be about the right size. For 50 hp and 4.5 foot diameter many have achieved 8 to 9 lbs thrust per hp. Google 'images shrouded propeller' for pics.

[Coyotes-R-Us]

cool thanks I will