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new and need advice

M

moparaddict69

Member
i am trying to sell my car and build a decent airboat but i am looking for some advice so i know what to look for when buying. my plan is for approx. 12'-14' hull, 2person drive seat, 2person pass seat, poly sheet on bottom, my main question is what motor, being a auto tech and knowing nothing about airplane motors really i am planning on building a sbc 350. is it a good idea to go with some electric components like electric water pump and fuel system or just stay with mechanical? what is the real gain of using a reduction drive box or is it ok to setup direct drive on an automotive motor? i will run a wood prop, size dont know yet. my uncle recently purchased a 16' fiberglass boat custom made by a local builder. his boat has a zz502, reduction drive, 12 blade carbon prop, he was saying i need a reduction drive or i will blow crank bearings left and right. he had a couple 500ci caddys in his old boat that blew up and a 383 chevy that he snapped his crank using direct drive, will i need to keep this in mind? any help and advice would be greatly appreciated.
thanks
 
There were at one time more aircraft engines on boats but today its about even, maybe a bit more auto engines. Your 350 SBC is very popular both in DD and Redrive configuration. As a DD engine it begs to be setup for low RPM torque and HP. With a Redrive unit it will run at higher RPM closer to what it saw in a car or truck and begs to be hot rodded in that direction. There is nothing endemic about the 350SBC and losing bearings or cranks in DD use. GM made a fine engine thats had decades of developement. The redrive unit will however let your engine develope more HP and in turn send more to the prop. Is a dollar value issue. Theres LOADS of boats rigged both ways. Waterthunder & Felber here are GM gurus. Just ask and youl get specific answers.

Electric water pump and etc are valued in the eyes of the beholder. They save the engine having to turn them but they cost $$ so its just a choice. Probably more boats do not have electric accessories.

Caddys are decent strong engines with a different set of issues than your SBC. I'd say at 14 feet you are on the edge for a stock SBC. You may want to look at smaller boat or building the engine up. In case you have the cash, Waterthunder sells already built units ready to drop in your boat. He runs a 600 HP SBC and its the quietest thing you ever saw on a boat. Probably the quickest as well.

You have come to the right place for help and advice, stand buy you ll get the best there is.

Scotty
 
Welcome to the group, I just finished my first boat and was wondering the same thing awhile back. If you plan on running any dry ground (the hill) you will probably want to go with the gear reduction. It's a money thing but trust me on this- it's well worth the extra cost. Gear box will enable you to reach the "power band" of your 350. As for the electronic components its a choice you have to make but remember there are 2 kinds of airboaters those that have sunk thier boat and those that are going to sink a boat. I got it out of the way real quick,did have to replace alot of electronics after that :( I stuck with all mechanical
personally. I have pics in my members photo gallery of the building process if you want to check them out. Just ask lots of questions there are some really fine folks here that will help out in any way they can.
SAFARI RICK
 
Every person that I have ever meet that switched from a DD to a gearbox all stated "I wish I did this years ago". Just start of with one because if you stick with air boating you will eventually buy one, plus think about how many less times you will be stuck because you are not a DD.
 
go with a sbc i have spent enough on my caddy to build 3 of them.but with that beeing said the caddy was my first airboat motor and i am partial to the big monster.
 
yep ! 14' is a little big for a sbc I'd go gearbox or a smaller hull either way although a 400sbc does a pretty good job DD with a 72x34 prop.With a gear box you'll need to hot rod the motor a little with good cam and heads dd you'll still need a good cam for the application.Me , being a ole ford motor man at heart , I left the chevy's for Cadillac's a while back.
 
i am a big mopar fan, i know i will probably catch crap for that but anyways i have a rebuilt 440 i could use. fresh rebuild about 500 miles ago in my car now. are there many if at all some parts and equipment that will work for me to use the 440 for an airboat. it is kind of hard to find mopar parts anymore so i didnt really want to use it, everyone and their grandmother have parts for chevys. with building a motor is it more important to focus on torque or rpm, do i need most of the tq at low end as a towing cam would do the best or what should i be looking for? also are there any mailorder catalogs or companies directed toward airboating that you guys can refer me to check out. thanks to everyone with the help i appreciate it
 
I would go with the chevy engines even if according to Stan there is nothing in them that is chevrolet anymore because we replace all the stock parts with aftermarket parts. If I had to vote i want torque lots of it comin in low and stayin awhile a nice flat long line of it.

I would definetly go with a reduction unit of some type. I would choose at least a 2.68 stinger super wide gear myself. Yep it will cost more but you can have a lot more fun with the boat. I wouldn't use a belt drive because they are heavy and the ratio is limited. slower turning props are gonna be the norm pretty soon so might as well get to it if your building one.

My best suggestion would be to buy one already built and figure out what you like and don't like about it and then build your own better, that way you may only have to build 3 or 4 till you get happier. Then you can sell the one you bought and help spread the disease to some other unsuspecting soul.
 
Hey Mopar, If you ask 100 people they would all give you a different answer on the perfect boat. I would suggest going with a 15ft Aluminum Hull, small block engine with belt reduction and a composite prop for your first boat. Please let me know if there is anything I can do to help.
 
I'm a closet Mopar guy at heart but them 440's are waaaaaaaaay to heavy and nobody makes a gear box for them.
 
Ditto. Now IF someone made a gearbox, and you just HAD to run a Mopar (Which what true-to-form Mopar guy wouldn't?) The torque curve would be pretty sweet. But what you need is 440 TQ and all aluminum 340 weight (I think it's called an LS1 LOL)

But in all honesty...If I were to come out of the closet, and build a sensible (read; Relatively budget) BB Mopar. I would avoid the tall deck (RB) with extreme prejudice. I would base my combo on the B motor, most likely the 400 block with a stroker 440 crank. The 470 combo comes to mind. Offset grind a stock 440 crank, put BBC rods in it with shelf pistons, and you have a compact/lightweight (By BBM proportions at least) and budget shortblock, that will free up the money to put a good set of aluminum heads on it, and you would have a bad lil beoch.
 
a Fellow airboater out of scramble town runs a 440 mopar with a gearbox and it runs good and he bleeds mopar.
 
I know it hurts but say it Mike you would build a Bad A@@ small block Ford before a 440. Since were getting goofy I love those SB Mopars I ain't never seen one of those on a airboat HE-HE.
 
Thanks for the reality check man.....I just had flashbacks of our conjured up destroked/long rod 440s w/B1 heads......Some of our munster stories are best forgotten. LOL
 
I remember the crank for it the one you did all that work on it was a work of art after you were done with it. How about our special designed DD OLDS airboat motor. We went crazy on that one, I still think it would work but at Idle it would be doing 20MPH.
 
I can say this because I'm a closet Mopar Man. Dodge guy's are wacko's they buy ton's of parts then store them in their garage for 20 years. I have done this myself and Felber will attest to that! I picture the Hemi being next to imposable to find at a reasonable price also the after market guy's don't pursue the Mopar market as aggressively and there are few if any parts available for the HEMI (so you must run the computer and all the stock electronics that go along with it) . Great Idea and if I can find one I will build one but then I need a special gearbox or an adaptor.
 
cntry141iq said:
I would definetly go with a reduction unit of some type. I would choose at least a 2.68 stinger super wide gear myself. Yep it will cost more but you can have a lot more fun with the boat.
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cntry141iq said:
I guess the good thing about my wife wanting me to finish renovations and landscapeing is I have had a chance to sit back and read your posts with no pressure. I have asked and you-all have answered a lot of questions. If I build the Direct Drive I will soon want a reduction unit, and I will have to change rigging and try to sell the old prop. I have the time to start saving for my reduction unit and prop. Thanks guys! :wink:
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This is from over a year ago before it caught on.

Waterthunder said:
I have learned everybody is obsessed about RPM’s. Most people don’t realize Horse power is derived from measuring torque the formula is (horsepower = rpm x torque / 5252) The gear box allows you to do two things. First is you can turn the motor at a higher RPM. Where a car motor makes it’s power because of it’s small cubic inches size and most of all the gear box is a torque multiplier. If you make 400 ft pounds of torque and run a 2.68 gear box your prop will see 1,072 foot pound of torque there is some loss of torque due to gear box inefficiency. I attack airboat car motors from a different angle than most people I don’t go for RPM’s I try to make 550 Ft pound of torque around 4,000 RPM and the let the gear box due the work. I argue this point at least twice a week. Don’t build a car motor to swing a prop more RPM’s build a car motor that doesn’t choke down when you add more pitch. That’s why I like the 2.68 to one. 99% of everybody doesn’t like this high ratio because most people think they must turn more RPM’s with a 2.68 box. Well I run a 2.68 and just keep adding the pitch most of my motors run so much pitch they turn a max of 5,800 RPM’s with a 2.68. I use the gear box as a torque multiplier not an rpm increaser. Most boats with this much pitch cruise the water from 1,800 to 2,100 RPM’s. A 2.02 to one box must spin the motor around 2,800 to 3,000 Rpm to develop the same thrust in order to cruise at the same speed. I have tested a 2.02 and a 2.68 box on the same exact boat to prove this point.
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