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I/O to OB conversion project?

Old 12-05-2018, 07:26 AM
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Default I/O to OB conversion project?

With all the rage being to repower to 400's, would it be feasible to take some used power (triple 300/350s) and hang them off the back of something like this:
https://www.offshoreonly.com/classif...aw-o73985.html

Straight bottom so no CG issues with the steps, boat is tired and has no power so it should be able to be bought cheap. Seal up the transom, add a bracket and hang the OB's. Redo the cockpit interior and reshoot the boat in a non-Baja theme or even just all white. You could have a 40 ft 70 mph boat when you are done!

Viable project or potential nightmare with no resale?
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Old 12-05-2018, 08:54 AM
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3, 300's/350's ain't gonna cut it on that boat. I'd think you'd need to do more to the transom than just seal up the old cutouts to support the bracket/OB weight.
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Old 12-05-2018, 09:22 AM
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Originally Posted by Knot 4 Me View Post
3, 300's/350's ain't gonna cut it on that boat. I'd think you'd need to do more to the transom than just seal up the old cutouts to support the bracket/OB weight.

Didn't they build the 40 with twin 575's as base power? Trip 350s is 1050 vs. 1150 I/0. Someone did this to a Tiger down in the Caribbean and I think it was triple 300s but I can't remember if it was a step bottom or not. Not sure if it was reported back on how it came out (good or bad).

The transom work I have no idea. The boat would be cool with triple roller coaster bolsters and a bench at the back.
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Old 12-05-2018, 09:25 AM
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You will want to add some transom knees to tie the transom into the stringers to support the weight of the OB's and bracket.
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Old 12-05-2018, 10:20 AM
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Originally Posted by Jupiter Sunsation View Post
With all the rage being to repower to 400's, would it be feasible to take some used power (triple 300/350s) and hang them off the back of something like this:
https://www.offshoreonly.com/classif...aw-o73985.html

Straight bottom so no CG issues with the steps, boat is tired and has no power so it should be able to be bought cheap. Seal up the transom, add a bracket and hang the OB's. Redo the cockpit interior and reshoot the boat in a non-Baja theme or even just all white. You could have a 40 ft 70 mph boat when you are done!

Viable project or potential nightmare with no resale?
Yes it will work
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Old 12-05-2018, 10:21 AM
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Originally Posted by Knot 4 Me View Post
3, 300's/350's ain't gonna cut it on that boat. I'd think you'd need to do more to the transom than just seal up the old cutouts to support the bracket/OB weight.
It should run good. They tend to run faster than equivalent power I/Os. I think it’s due to the CG being further back, and possibly due to less power loss to the prop.
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Old 12-05-2018, 10:45 AM
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350's with hotboxes then!
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Old 12-05-2018, 10:46 AM
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Less weight is a big factor. Can also raise the X-dimension on the fly with some jack plates.

I am curious as to the cost myself to convert to outboards. Anybody know what the guy paid to convert that 31 Cigarette Bullet to outboards that is for sale?
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Old 12-05-2018, 10:51 AM
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It works out great. Done it twice to I/o boat.
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Old 12-05-2018, 10:59 AM
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It is all about CG, CB, and transom strengthening. When I converted my 35' Cigarette Awesome to a 28' outboard center console. the new transom was the center of my work. It was supported by the stringers and knees, by the motor well design, and by major tabbing to the bottom, sides, and deck. The layout of the console, fuel tank, T-top, etc. was driven by the new balance point. A lot of work, but I would do it again.
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