Direct Drive - Pros and Cons Please

Automotive powered airboat discussion.
Nooner
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Direct Drive - Pros and Cons Please

Postby Nooner » Wed Apr 11, 2018 3:50 pm

I am thinking about putting a direct drive boat together because i literally have all the parts for it but i have never had a car engine boat, all i have ever had were aircraft engine boats.

Looking for information on the pros and cons of a direct drive and the potential "pit falls".

Keeth1123
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Re: Direct Drive - Pros and Cons Please

Postby Keeth1123 » Wed Apr 11, 2018 6:22 pm

I used to have a DD 350 boat. I was lucky enough to put it together with the help of my brother and the people on this site. I never expected it to do much, but the boat got me around the lake and did run some dry ground to my surprise. It was good on gas to.

The Chevy 350 was stock and purchased from Nomad41 on here. We put an RV cam in it before putting it on the boat. Had it matched with a 4 blade, 72” prop.

Personally, I think they are great,economical boats that are fine as long as you don’t plan to run primarily dry ground. Normally I just spun mine around on the edge of where I was parking.

The biggest load I had in the boat was three people, extra battery and tool box for the third guys boat that broke down. Boat ran fine and had no issues riding out with the load.

:old_glory:

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Deano
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Re: Direct Drive - Pros and Cons Please

Postby Deano » Wed Apr 11, 2018 6:31 pm

Your question is to general in nature to offer much constructive input without more info.
Also, what you've run in the past, that is the source of your comparison would help.

Pros -
Inexpensive:
1- acquisition
2- to maintenance
3- to operate

Cons -
Limited:
1- hull size
2- toting capacity
3- run dry ability
4- All of the above, which comprises the 'biggest pitfall'; lacking the power/thrust to do what you want do with the boat.

If you have everything to do it and share what that amounts to, we will have some information on which to comment.
There is a colossal difference between a 327 on a 15' hull and a wood prop, and a 500 Cadillac on a 14' hull with a composite prop.
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
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kwanjangnihm
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Re: Direct Drive - Pros and Cons Please

Postby kwanjangnihm » Wed Apr 11, 2018 8:16 pm

Keith I fixed your youtube video bro! Top of the ridge! :thumbleft:
" I don't care who you are back in the world, you give away our position one more time, I'll bleed ya, real quiet. Leave ya here. Got that? "

Keeth1123
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Re: Direct Drive - Pros and Cons Please

Postby Keeth1123 » Wed Apr 11, 2018 8:53 pm

kwanjangnihm wrote:Keith I fixed your youtube video bro! Top of the ridge! :thumbleft:



Thank you!

That’s my highschool boat. Everyone said it wouldn’t run any dry. It barely
Made it but it got up there lol
:old_glory:

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Re: Direct Drive - Pros and Cons Please

Postby flcracker9 » Thu Apr 12, 2018 8:08 am

Nothing wrong with a DD, especailly as an entry level boat. For those on the fence when purchasing their 1st boat, it's an option to look at a DD from a cost perspective, rather than spending big $$$ and then deciding it's not for you, or you never have time to use it. If you go the DD route, just gotta keep em as light as possible if you plan to run any dry.
12' Open Palm Beach, IO-0470-L 260hp, 72" NGQ

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Re: Direct Drive - Pros and Cons Please

Postby flcracker9 » Thu Apr 12, 2018 8:14 am

[/quote] That’s my highschool boat. Everyone said it wouldn’t run any dry. It barely
Made it but it got up there lol[/quote]

My Son's DD has been up that ridge several times with 2 people on board (12' Big O, 350 chevy, 70" Q). Some folks think it can't be done, but when you're on a budget, you work with what you have!
12' Open Palm Beach, IO-0470-L 260hp, 72" NGQ

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John Fenner
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Re: Direct Drive - Pros and Cons Please

Postby John Fenner » Thu Apr 12, 2018 9:09 am

If you search on DD builds there are quite a few threads on the best combination for torque and on a budget builds.
I never finish anyth,,,.

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Re: Direct Drive - Pros and Cons Please

Postby John Fenner » Thu Apr 12, 2018 9:12 am

I never finish anyth,,,.

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kwanjangnihm
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Re: Direct Drive - Pros and Cons Please

Postby kwanjangnihm » Thu Apr 12, 2018 10:48 am

Nooner what are your engine choices at this point? :scratch:
" I don't care who you are back in the world, you give away our position one more time, I'll bleed ya, real quiet. Leave ya here. Got that? "

Nooner
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Re: Direct Drive - Pros and Cons Please

Postby Nooner » Thu Apr 12, 2018 6:09 pm

So this is where i am and what i have to go with. The hull is a 12' x 7' fiberglass step hull with a full aluminum deck on it and i have a Ford 390 engine just sitting around that i can use. I also have all the materials for the rigging and set-up including rudders. the only thing that i would need to buy would be a prop adapter and the prop itself.

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Re: Direct Drive - Pros and Cons Please

Postby flcracker9 » Fri Apr 13, 2018 8:47 am

Nooner wrote:So this is where i am and what i have to go with. The hull is a 12' x 7' fiberglass step hull with a full aluminum deck on it and i have a Ford 390 engine just sitting around that i can use. I also have all the materials for the rigging and set-up including rudders. the only thing that i would need to buy would be a prop adapter and the prop itself.


That will be a pretty heavy engine for a DD, just saying (that 390 is 100lbs more than a 350 & 50-75lb more than a 500 caddy), but if you're content just cruzing around in the wet stuff, go for it. My suggestion for a prop would be a 70" - 72" Q
12' Open Palm Beach, IO-0470-L 260hp, 72" NGQ

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Deano
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Re: Direct Drive - Pros and Cons Please

Postby Deano » Fri Apr 13, 2018 10:01 am

The intrinsic problem with using just about any big block Ford is they generally don't have an attractive power/weight ratio.
In other words they are freakin' HEAVY for the power produced. The 390 being among the smaller of them, doesn't lessen that reality.

I question if your step hull would have enough freeboard to allow for much of a comfort level during 'normal use'.
By nature, step hull designs are among those least suited for using an abnormally heavy power plant.

Guess it all depends on what you want to do, and where you intend to do it. Such a setup, would definitely not be for the novice.

Were it me personally, I would weigh which I preferred (the hull or the engine) for the use I had in mind, and then replace the other.
Either the hull or the engine could make for a fun, reasonably inexpensive means of getting on the water.
IMHO though, those specific pieces would not compliment each other and/or make a particularly good combination.

Not to say that it couldn't be done; if 'unique' were a measurable part of the quest, it damn sure would be that. :)
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but it is not the path to knowledge; it has no place in the endeavor of science."
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kwanjangnihm
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Re: Direct Drive - Pros and Cons Please

Postby kwanjangnihm » Fri Apr 13, 2018 2:25 pm

Deano wrote: In other words they are freakin' HEAVY for the power produced. IMHO though, those specific pieces would not compliment each other and/or make a particularly good combination.


x 2 :salute:
" I don't care who you are back in the world, you give away our position one more time, I'll bleed ya, real quiet. Leave ya here. Got that? "

SeatCover
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Re: Direct Drive - Pros and Cons Please

Postby SeatCover » Sat Apr 14, 2018 9:39 am

Get a 4 banger aircraft motor and it will outperform that 390 all day and won't sink the first time out.
12' Cut Gilleo, Angle Valve 0-320, 72" Whisper Tip. Goes wherever I point it. :florida:

Nooner
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Re: Direct Drive - Pros and Cons Please

Postby Nooner » Sun Apr 15, 2018 3:23 pm

Deano wrote:The intrinsic problem with using just about any big block Ford is they generally don't have an attractive power/weight ratio.
In other words they are freakin' HEAVY for the power produced. The 390 being among the smaller of them, doesn't lessen that reality.

I question if your step hull would have enough freeboard to allow for much of a comfort level during 'normal use'.
By nature, step hull designs are among those least suited for using an abnormally heavy power plant.

Guess it all depends on what you want to do, and where you intend to do it. Such a setup, would definitely not be for the novice.

Were it me personally, I would weigh which I preferred (the hull or the engine) for the use I had in mind, and then replace the other.
Either the hull or the engine could make for a fun, reasonably inexpensive means of getting on the water.
IMHO though, those specific pieces would not compliment each other and/or make a particularly good combination.

Not to say that it couldn't be done; if 'unique' were a measurable part of the quest, it damn sure would be that. :)



Well the hull is what I’m wanting to get on the water, the motor is just something that I have sitting here. What engine would you suggest?

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Deano
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Re: Direct Drive - Pros and Cons Please

Postby Deano » Sun Apr 15, 2018 5:02 pm

I would have to agree wholeheartedly with SeatCover's recommendation of a 4 cylinder A/C engine. Everything he said is factual.
It may be worth noting that power wise, the weight penalty to be paid for more power is negligible while you're talking 4 cyl aircraft.
You surely don't need an O-360, but while the power can vary widely, the weight is not nearly as big a swing as the power may be.
"The suppression of uncomfortable ideas may be common in religion and politics,
but it is not the path to knowledge; it has no place in the endeavor of science."
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