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-   -   Tunnel hull for 15hp (http://www.saltycajun.com/forum/showthread.php?t=31807)

70hptiller 05-27-2012 04:17 PM

Tunnel hull for 15hp
 
I am considering putting together a tunnel hull rig. I would like to use a little 15hp Mercury. I have seen the abuse they will take and I like how light they are. Typical load would be two people and a battery. Any suggestions on what size hull? Speed is not important, but being able to plane out is.

MathGeek 05-27-2012 05:37 PM

Quote:

Originally Posted by 70hptiller (Post 438489)
I am considering putting together a tunnel hull rig. I would like to use a little 15hp Mercury. I have seen the abuse they will take and I like how light they are. Typical load would be two people and a battery. Any suggestions on what size hull? Speed is not important, but being able to plane out is.

I'd say to keep the total weight under 800lbs (boat, motor, battery, passengers, gear) and you've got a great chance at getting it up on plane in most conditions. Two 250 lb men doesn't leave much weight left for the boat, motor and gear, so you probably should think pretty light. Two 150 lb people leaves a lot more weight for the boat and gear. Optimizing the prop selection might get you to 900-1000 lbs depending on the hull, conditions, and weight distribution.

I used to put my 16 ft. alumacraft up on plane all the time with a 9.8 hp Nissan, but it was when my kids were little and we carried a lot less gear in the boat, and lived close to sea level. Now, fully loaded including people and gear, the rig is often just over 1000 lbs and I need the 20 hp Nissan to put it up on plane. Sometimes with a big load of fish and three grown men (1200-1300 lbs total), I can't get up on plane or have to do some tricks shifting weight around to get the boat to plane. Of course, due to the thin air in CO, I'm probably not getting the full 20 hp. But on one occasion in LA last year, I couldn't get it up on plane and I estimate the total weight was 1300 lbs once we'd caught a mess of fish.

Ray 05-27-2012 07:16 PM

I would not go shorter than 16 ft. long. 36" bottom also.
It won't be fast, but can get you thru some shallow stuff.
An old guide that usta hunt at the Hackberry Hilton used an 18 X 36 tunnel hull with a 9.9 HP on back.
Slow boat, but didn't have the weight of a 25 or 40 hp motor. It did a lot better than I thought it would for such a small motor.
You just have to prop it right to push the weight. Don't want to overload the engine and wear it out early.

70hptiller 05-29-2012 09:41 PM

Thanks for the suggestions. I live in Tennessee so a Southfork wouldn't be too easy to get. Is there a preference between Alweld and Weldbilt? Does one company have a better tunnel design than the other?

Raymond 05-30-2012 11:14 AM

Quote:

Originally Posted by 70hptiller (Post 439528)
Thanks for the suggestions. I live in Tennessee so a Southfork wouldn't be too easy to get. Is there a preference between Alweld and Weldbilt? Does one company have a better tunnel design than the other?

Errebody says southfork has best factory tunnels,idk. Doubt you will get a 15' factory tunnel but 16x36 should work with 15hp propped right and vented. I run a weldcraft that is self vented and like it alot. You should be able to find a dealer off the companies websites but don't expect much knowledge up there about a coonazz boat.;)

70hptiller 05-30-2012 11:29 AM

I'd like to run a 1836. I can get to a weldbilt dealer pretty easily, alweld would be a little more trouble but if they are a better running boat I'll make the drive.

Raymond 05-30-2012 01:35 PM

Quote:

Originally Posted by 70hptiller (Post 439763)
I'd like to run a 1836. I can get to a weldbilt dealer pretty easily, alweld would be a little more trouble but if they are a better running boat I'll make the drive.

stay away from the semi v hulls, they aren't much with a tunnel in them.
15hp will not push an 18', min would be a 25hp on 18x36
Where u located in E Tenn? Running mud or gravel over there?

70hptiller 05-30-2012 09:08 PM

I am northwest of Knoxville. I need a boat for duck hunting and frog gigging. We run mud, but its all hard bottom since everything around here is a reservoir.

I had a 20hp Go-Devil, but it was a pain to manuever and no reverse. Once you hit bottom you're stuck. We can get most places with a 20hp Mercury with shallow drive, but its slow going since you have to idle everywhere.

coastalobsession 06-03-2012 06:11 PM

Try to find a 14ft aluminum with a tunnel

70hptiller 06-03-2012 07:51 PM

Can I ask the reasoning for a 14' boat? I have never seen one of these rigs run in person, so I am trusting the advice of the members of this forum.

A 1436 weighs 230 pounds, a 1636 weighs 255 pounds, and a 1836 weighs 270 pounds. Will a 15hp not push a longer boat because of this additional weight? Or is it something else?

davidkyle323 06-03-2012 07:59 PM

The longer the boat the less it will sink into the water when not on plane, but the longer the boat the more drag created when on plane for top speed. Tunnels usually work better the longer they are but never had experience with one with that low of HP. I have had them with 25hp and I now have a southfork with a 40. My old tunnel was a 14 foot and it drafted a lot more water than my 16 I have now. But it was also a heavy made boat.

70hptiller 06-05-2012 01:14 PM

Thanks for the advice, David.

70hptiller 06-06-2012 10:58 AM

I'm wondering if a 25hp would be a better choice. I was gonna get a 15hp since you can pick them up by pushing down on the tiller handle for jumping logs and shoals, but if it won't push the boat I might need to get a 25hp instead?

davidkyle323 06-06-2012 05:41 PM

I would go with the 25 and the longer boat if it was me. The longer boat will offset the weight of the motor. I can get up in shallower water with my 40 than with my 25 so power does make a big difference, the faster u can get on plane the better off u are. I know a lot of people with 25 on a 16 foot tunnel and they work great!

davidkyle323 06-06-2012 05:42 PM

Are u planning on buying a new motor or a used one??

70hptiller 06-06-2012 05:47 PM

Used. Most likely a early nineties model.

davidkyle323 06-06-2012 06:30 PM

Sounds good 2 stroke is the way to go, light.

Raymond 06-06-2012 08:37 PM

Quote:

Originally Posted by 70hptiller (Post 443408)
I'm wondering if a 25hp would be a better choice. I was gonna get a 15hp since you can pick them up by pushing down on the tiller handle for jumping logs and shoals, but if it won't push the boat I might need to get a 25hp instead?

That makes more sense! Would go with 18x42 with a 25 3 cylinder yamaha, those wide open reservoirs can get ruff and a 36 would be dangerous. A 40 would be tits and shouldnt be that big of a $ difference.

cmcnabb 06-06-2012 09:18 PM

My buddy is selling a 3 cyl Yamaha 25 with 40 carbs and intake work if your interested. He has it in an 18 42 with a vented tunnel. It will run in wet dirt

davidkyle323 06-06-2012 09:24 PM

Yea I agree with the 42 inch bottom


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