transoms i/o to outboard

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circle hook

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hello i am getting a 20 foot gradywhite with a 170hp i/o i also have a dual stainless outboard bracket. Can i cover the out drive hole in the transom with the bracket and replace (2) outboards adding up to the 170HP say like (2) 85 HP outboards.
 
Bob_VT

Bob_VT

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Re: transoms i/o to outboard

You need to read the USCG building regulations. There are significantly different calculation formulas for I/O vs outboard.
 
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circle hook

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Re: transoms i/o to outboard

where can i find these uscg building regulations for grady whites thanks bob
 
NSBCraig

NSBCraig

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Re: transoms i/o to outboard

Yeah you can do what your thinking, as for the coast guard thing it doesn't matter at 20' and over.

Post some pics of your project.
 
DuckHunterJon

DuckHunterJon

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Re: transoms i/o to outboard

Do some searching for I/O to OB conversion. It's no small feat, but others have done it.
 
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Chris1956

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Re: transoms i/o to outboard

How about hanging a single 150HP Outboard on it? It will be lighter and give better performance. Maybe a kicker to get home with.

Why do you want to get rid of the I/O? An OB hull will have better interior space, but the conversion will be a fair amount of work.
 
oops!

oops!

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Re: transoms i/o to outboard

people that have done these conversions are not allways happy with the results...
 
zagger

zagger

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Re: transoms i/o to outboard

I/O transoms are build to different specs, the torque is absorbed through the stringers (engine sits on them) and transom. In a OB the sides/deck and transom provide the load area. Aside of plugging the holes you should add bracing between transom and stringers. The old HP rating would no longer apply as the power loads will be distributed differently on the hull.
 
oops!

oops!

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Re: transoms i/o to outboard

not only that the cg changes considerably
 
S

Solittle

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Re: transoms i/o to outboard

Spend some time here using the Search function before you leap. There are quite a few posts from those who have done it - - many were not pleased with the results.
 
spdracr39

spdracr39

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Re: transoms i/o to outboard

Sounds like it would be easier to buy a different hull that is set up for an outboard. It would have to be cheap if the motor was bad or you could sell the motor your not going to use and get some money beck.
 
S

Sprky

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Re: transoms i/o to outboard

Do it and don't look back.

Make sure to repair the transom properly and add knees to the stringers.

When done right, and going back with the same hp, it always makes for a boat that performs and handles way better than what you started with. The only reason anyone would be unhappy is if they dicked up the job to begin with.

Moving the cg aft is a good thing, especially the pig you are repowering. (Yes it is a heavy boat)........ Don't let anyone tell you otherwise.
 
NSBCraig

NSBCraig

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Re: transoms i/o to outboard

It's not like your boat wasn't designed to be equipped either way.
They came with outboards on brackets, new ones have the bracket built in.
Go for it.
 
C

circle hook

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Re: transoms i/o to outboard

I am getting the grady white for free and the double stainless bracket I got for doing a job for some one so thats also free and I have a twin shifter/control fit for mercury so I will stick with mercurys and I thought the floation of the bracket also took weight off the transom but adding knee braces's to the stringers makes sence sounds like a go Thanks Bob
 
oops!

oops!

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Re: transoms i/o to outboard

Sprky said:
Do it and don't look back.

Make sure to repair the transom properly and add knees to the stringers.

When done right, and going back with the same hp, it always makes for a boat that performs and handles way better than what you started with. The only reason anyone would be unhappy is if they dicked up the job to begin with.

Moving the cg aft is a good thing, especially the pig you are repowering. (Yes it is a heavy boat)........ Don't let anyone tell you otherwise.
Click to expand...

the csg is higher not aft. the weight is aft.

NSBCraig said:
It's not like your boat wasn't designed to be equipped either way.
They came with outboards on brackets, new ones have the bracket built in.
Go for it.
Click to expand...

i/o s hulls and ob hulls are totally different molds.....they were not the same.

ill say again....people that have done this conversion have not been happy with the results
 
S

Sprky

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Re: transoms i/o to outboard

LOL........don't quit your day job!



Weight shift formula:

Weight shifted Δ CG (change of CG)
------------------ = -------------------------------
Total weight distance weight is shifted
 
oops!

oops!

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12,932
Re: transoms i/o to outboard

i think you have some things confused....

shifting the weight from the bottom of the boat and 3 feet forward to the top of the hull aft. will change the CG....but not the way you are implying it....
 
B

Bamaman1

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May 15, 2011
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Re: transoms i/o to outboard

In my travels, I see marine salvage yard after yard full of fantastic junked inboard outboard hulls--like the 22' Sea Ray deep V hull bowriders from the late 1970's, Wellcrafts and other great brands. If solid, these hulls can be either re-engined with a modern inboard outboard unit or switched over to a big 4 stroke outboard.

Changing over to an outboard is no great feat if you use a custom built external motor mount--usually built from aluminum. The motor mount builders are easily found on the internet, and the prices are quite reasonable.

If anything, a 3' long motor mount will lower the center of gravity--and make it ride like it's longer. The challenge is glassing over the I/O hole in the transom.

That's the least expensive method of having a fantastic quality boat.
 
NSBCraig

NSBCraig

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Re: transoms i/o to outboard

oops! said:
i/o s hulls and ob hulls are totally different molds.....they were not the same.
Click to expand...

Are you sure about the oops? Grady White has different molds now since the bracket is part of the hull but I'm pretty sure they were the same back then. There really is no reason for the difference in the mold so why would they?
 
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