New Boat PLEASE help!

[aewrigh]

Hey guys, just joined this forum and just last week I discovered the world of mini-airboats. I have already ordered a custom built, all eighth inch, aluminum jon boat from a builder. The boat will be 12 foot long, 48 inch bottom, and will have 20 inch sides and transom. I was originally going to put a mud motor on the boat but with the tall transom I would pretty much be limited to a longtail with small engine. I could go with a 23 hp surface drive and go that way but that engine weighs over 200 lbs. I think a little airboat would be sweet. By the way, my boat will have a slick bottom with cross bracing, a bench in the back, and a 3 foot long deck up front. What could I do with this boat? Like I said, I am completely new to this so any help would be greatly appreciated!

[Papee]

What area do you live? What do you plan on using it for? A 48" bottom isn't very wide but will work if you keep everything light.

[aewrigh]

I live in southeastern Oklahoma. I plan to use the boat to go up the creeks for limblining, duck hunting, deer hunting, fishing, etc. I also plan to go up a river where I live that is very silted in at the mouth. Only airboats can get in. How light are we talking? I think the hull will be fairly heavy being all 1/8 inch. 350-400 maybe? I don't look for it to get on plane with 3 guys and a bunch of gear but I would still like to get up the creek at a decent clip. It'd be nice if it would run 20 or so with 2 guys and an ice chest of catfish. I have seen small fans used as pushers for bowfishing boats and they move pretty good for the hp to weight ratio. I just have no idea where to start as far as what motor, prop, reduction, etc? I am very capable of fabrication and can weld steel and aluminum. Also, what would I be looking at as far as cost for a whole setup? Mainly looking for the price of the motor and fan equipment. I can get conduit for free, whether it be emt or rigid aluminum. Any help would be greatly appreciated. I am on the fence between attempting this or just getting a mud motor for it. I am the type of guy who wants something because nobody else around me has one though. I think I am the only guy with a rokon trailbreaker in oklahoma lol. It was expensive but have never seen another around in my neck of the woods. I also enjoy building stuff. BTW I am also the type that highly prefers to buy new stuff as opposed to used so that it is as trouble free and reliable as possible. I will have the hull in a couple weeks so I really need to decide! Please help me out.

[bbb]

My advice is to try the mud motor first. It's a lot easier to sell a mud motor than a fan cage with motor.

The mud motor is a lot more versatile, and will produce better speeds.

[papajack]

You might want to search "air jonboat" and see what some option are. In my opinion, you may not be happy wanting to get 20 mph with two guys and gear in a heavy jonboat with cage motor and prop. Papee on here is a great info source. Really listen when he responds

[Papee]

If your bottom is 48" you most likely have room to run a 52" prop after the cage is made. Depends on how far your sides are angled. This means you could run up to 40-50 hp something like a 4A084. You could run a 35hp Briggs with reduction but you'd get into a bit of cash with a reduction setup. It all depends on how deep your pockets are. If you're not already aware I'm an 4A984 guy, I've been running one direct drive on my 14 ft boat with a 5' bottom for years now. It's a very reliable motor and pushes around 40hp. My boat is also thick aluminum and weighs about 400lbs. I can plane with two hefty people in and some gear. I rarely run more than 2800 so reliability is good seeing the motors were made to run a constant 3600 rpm. I use my boat a lot so I go a different route than most.

As far as speed, I have done a few Jon boats for friends and they did not plane out but the speed was up there because of the way they ran in the water. They just didn't run full throttle so the front wasn't pushing as much water. Some times if a small boat doesn't plane it is better to go at a slower rpm and you actually go a bit faster. It can be done, when I first got my boat it was 15'8" long, I had nothing in it other than my seat. It had a 18hp Briggs on it with a 42" prop and it did plane in skinny water. Weight is a big factor, when you start adding batteries and more seating it adds weight.

[aewrigh]

Where would I acquire one of the 4a084 engines? I am guessing it is a small plane engine? How much would I be looking at spending on an engine and prop? And as far as using a briggs, this reduction you talk about......could I not get the same effect with cogged belts and pulleys? Papee, does your boat almost run dry? My boat will be 5-5.5 feet across the top so I wouldn't see a problem in running a 52 inch prop. Thank you for the help. I appreciate it greatly. I am wondering if I could do this cheaper than spending 3500 on a mud motor?

[papajack]

I will chime in on the Briggs, I have two (but that is changing as we speak - more on this on another thread). A Briggs Vanguard 35 hp new around $2350, Arrowprop reduction new around $ 750, Prop range new IVO around $350 - new Whirlwind Razor X Core around $900, rigging, rudders. electrical , guages steering, throttle and pedal, etc. misc stuff probably another $500+.

And that begins the journey through this sickness...
It's all GOOD!!!!!!!!!!!!!!!!!!

[Papee]

The 4A084 is an Army surplus engine that the experimental aircraft guys have been using for years. My boat actually had one of these on when it was built back in the early 80's. It's had many engines on since then including a Buick v6. I haven't been keeping up with the supply of the 4A084, Chuck at Airboat Pros may have one or know where to get one. I got mine used from Chuck and I think it cost around $180 to have it shipped from Fla to PA. As far as cost, you can come across used ones starting at $250 but you don't know what you are getting. It's best to find someone that is know by other folks either here or on SA to be safe.

Sorry about my memory as it's been a while. The prop adapter came from Arrow Props, mine was the first made by them. I am also running a 52" wooden prop from Arrow props and I'm very happy with it. You'll have to call Bill at Arrow Props for pricing on the prop and hub. You could very realistically have your motor, prop, and, hub for around $1000. My stainless steel headers also came from Chuck at Airboat Pros again I'm not sure of the price on them.

I've never really tried to run my boat "dry" I never intended it to be out of the water. I have run in in the snow. The only time mine has been on land was the time I lost an edge and slid up on land and hit a tree.

AS I've said before, It all depends on how deep your pockets are. Mine have holes in them so I have to do everything with little money. This is mainly the reason I started this site, to show people that they can get into airboating and don't have to break the bank.

[aewrigh]

I am assuming that your estimate of 1000 is for used parts? That doesn't bother me as long as the engine is in good condition and runs good. The only thing about the 4ao84 is I know nothing about them.....are there some good sources for information on them or manuals you can get a hold of? I guess I will be on the lookout for a motor. I have had no luck on craigslist or ebay yet. My pockets don't neccessarily have holes in them but I have so many other projects going on, there isn't much left to put towards this one. I was wondering about the narrow bottom of my boat and was thinking about mounting the engine near the bottom of the boat and running long v-belts to the prop. Have you seen this done? I just don't know about the weight being that high. This would be more of an issue if I went with a vanguard. If I could find a 4ao84 I would just run direct drive for simplicity. Does thrust at Idle become an issue for you? How much propulsion do you have at idle? I will have the boat within 2 weeks and would like to start building a stand but I don't see being able to do it without the motor for mock-up.

[Papee]

Yes the $1000 would be considering a used motor. A new motor can get up to $1800 itself. These motors are very similar to a VW motor, they are a 4 cyl horizontal opposed engine and very easy to work on. There is a forum on these engines. http://miniairboatassoc.com/forum/fo...e-4A084-engine

Keeping the weight low is a good idea but I wouldn't over-think it. In the case of a setup needing a reduction it would be fine to mount the engine lower. Some setups are made to place it this way although not by much. Longer belts cause more slippage and are harder to keep tight. If going with a direct drive setup I wouldn't worry about keeping the setup low, just set it up the way it needs to be to clear the transom. Just keep the seating lower, that is where most of the weight will be.

[aewrigh]

Well I appreciate the information and when I get the boat and find a motor I will definitely be back. Keep an eye out for a motor for me. (918)424-2NIne 42, Thanks, Aaron

[buster]

aewrigh,

I spotted this craigslist ad for two 084 engines "New in crate". That's the way I bought mine and it worked out great.
The price was $450.00 but the location was Walhalla. I have no clue where that is, but the phone listed is (864) 784-0518.
The ad was posted 9-4-12, so they may be gone, but it's worth a call. Good luck,

Dave

[aewrigh]

Thanks dave I'll give them a call

[aewrigh]

ok I called him and he wants 450 for one and it would probably cost me 150 to 200 to get it shipped. However, a buddy of mine ran across a guy in Oklahoma city (2.5 hour drive from me) that has 2-3 of them. He is selling them as used and said they might be government refurbished? He said that he got them from a government auction and that they were in crates. He said the crates are about gone and they are sitting out in the weather but said they haven't been there for long. I have him talked into $200 for one of them. How does this sound Papee? Is it too big a gamble or a steal?

[aewrigh]

BTW, if I go to get one, what all do I need to check out? He said he has never fired them up.

[Papee]

Compression check would be ideal but if you can't, look for leaks, check the oil, and try to pull it over with a rope. It should be very hard to pull the rope. Also pull the plugs and look to see how they were firing. While you have the plugs out check for spark. it would be very easy to start one on the ground, just take a gas can and hose with you.

[aewrigh]

I am guessing they have a mechanical fuel pump? What kind of compression should see on a good sound cylinder?

[buster]

If you decide to go with the "New in Crate" engine, as I did, you probably will get an engine with all the factory tin, a 24 volt starter, all painted olive drab, and even a service manuel. However if you have it shipped, you won't get to check anything until you recieve it. I don't think it is a bad thing that he didn't start it, as I believe they are prepped for long storage when they leave the factory. I was very satisfied when I got mine. Even though It cost a bit more, having a totally new engine seemed better than starting out with a used one like I did the first time around I put money into fixing it equal to what the new engine cost me, and I ended up replacing it anyway!

I think that engine is in S. Carolina. I would recommend you check UShip for bids to transport it for you. I had an airboat shipped from Minnesota to Colorado, and I was very happy with the job, and the cost.

Good luck,
Dave

[aewrigh]

the ones here in oklahoma have all the tin, starter, etc. and they are indeed olive drab. 200 and a bit of gas sure sounds a lot better than 450 and possibly 200 shipping.