Converting a missile to outboard

Designs for inboard or outboard power

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lakecat
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Converting a missile to outboard

Postby lakecat » Mon Feb 20, 2017 6:50 am

Hey folks, it's been a while. I've moved to Chicago and I've realized that the inboard I had been planning to build might not be the best boat now. There are lots of shallow waters here and my brother just bought a 19 foot deck boat. So I'm thinking about a little 16 foot outboard ski boat would fit the bill a little better. The rebel could be lengthened but has a pretty narrow beam. So I'm wondering if a missile could be rigged with an outboard? Does anyone know the depth of the transom?

I would pick the malahini but I'm looking for a design with a lot of tumblehome.

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Bill Edmundson
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Re: Converting a missile to outboard

Postby Bill Edmundson » Mon Feb 20, 2017 7:15 am

lakecat

I think it could be done. But, it would depend on how big of an outboard.

Bill
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lakecat
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Re: Converting a missile to outboard

Postby lakecat » Mon Feb 20, 2017 7:22 am

I'm thinking about a 90 HP etec. I definitely don't want to under power the boat but I just want to pull skiers tubes etc and have fun with a few people on board. I'm assuming once I would shrink the motor stringers the hull would be close to the weight of a malahini. Am I in the right ballpark?

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Bill Edmundson
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Re: Converting a missile to outboard

Postby Bill Edmundson » Mon Feb 20, 2017 8:44 am

Lakecat

Anything you saved on the stringers will go right back in to reinforce the transom and add a splash well. Power wise, I think you're about right.

E-Tec 90 weighs 320#. E-Tec 90 HO weighs 390#. Yamaha 4 stroke 90 weighs 366#. I don't know what a 5.0 liter engine + vee-drive would weigh.

I'm not a boat designer and I don't speak for Glen-L. This is just my opinion.

Bill
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chugalug
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Re: Converting a missile to outboard

Postby chugalug » Mon Feb 20, 2017 9:12 am

:D How about using powerplant and drive from Sugar Sand jet boat or equivalent? :roll:
Working on regular-sized Bo-Jest


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Nova SS
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Re: Converting a missile to outboard

Postby Nova SS » Mon Feb 20, 2017 9:43 am

If I remember correctly believe someone did this exact thing, converting a missile to an outboard, several years back and posted about it here.

This is in one in the customer photo archive on here

http://www.glen-l.com/picboards/picboar ... 1086a.html

lakecat
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Re: Converting a missile to outboard

Postby lakecat » Sat Feb 25, 2017 8:17 am

So, would I have to build a motorwell at all or would a bracket work?

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Bill Edmundson
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Re: Converting a missile to outboard

Postby Bill Edmundson » Sat Feb 25, 2017 9:05 am

I would do a well. If water does slosh over the transom it can go back in the lake, not just swamp your boat.

Bill
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BillW
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Re: Converting a missile to outboard

Postby BillW » Sat Feb 25, 2017 12:43 pm

A bracket or "jack plate" type mount for a large outboard would place huge loads on the transom. In some installations
the motor is 6 inches or more behind the transom.

Therefore, you would have to strengthen the transom as if you were building a motor well in the first place. And you would still
need the self draining feature.

I think the Missile would be excellent; just be sure to angle the transom. The one in the picture would be ok for top speed,
but would not pull a skier out of deep water.

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hoodman
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Re: Converting a missile to outboard

Postby hoodman » Sat Feb 25, 2017 1:00 pm

What about the stilleto?

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Mr Hot Rod
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Re: Converting a missile to outboard

Postby Mr Hot Rod » Sat Feb 25, 2017 1:48 pm

I found this photo on screamandfly.com. Transom is 90 degrees but the center section was inset at 15 degrees. This solves the outboard mounting issue and has a very clean look.

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sproggy
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Re: Converting a missile to outboard

Postby sproggy » Sun Feb 26, 2017 3:46 am

It's interesting to see a picture of that 'split transom' as I have been toying with a similar arrangement. However I was concerned about the stepped transom trailing edge and how it would affect the boat's performance on the plane. Any views on that? it must make some difference.

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Mr Hot Rod
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Re: Converting a missile to outboard

Postby Mr Hot Rod » Sun Feb 26, 2017 6:26 pm

We may have to get some input from Glen concerning the stepped transom trailing edge.

Or find another solution ...

Here are some photos from SJC's Tunnel King build. The transom is inset but the center section's bottom edge is flush with the transom edge.


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BillW
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Re: Converting a missile to outboard

Postby BillW » Sun Feb 26, 2017 8:29 pm

That offset in the bottom at the transom is not uncommon with high performance outboard boats.
For examples, see http://www.raveauboats.com

The offset provides a little "after plane" surface area; very little in the case of the yellow boat.

That yellow boat obviously needs more, therefore the large adjustable trim tabs, or after planes.

Bill

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sproggy
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Re: Converting a missile to outboard

Postby sproggy » Mon Feb 27, 2017 1:33 am

BillW wrote:That offset in the bottom at the transom is not uncommon with high performance outboard boats.
For examples, see http://www.raveauboats.com


Lovely looking boats, those.


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