Transom motor mount holes, before or after fiberglass?

Outboard designs up to 14'

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cmahler
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Transom motor mount holes, before or after fiberglass?

Postby cmahler » Wed Aug 23, 2017 9:34 am

I'm trying to figure out when outboard motor mount holes should be drilled in my transom. The instructions don't state whether this should be done before or after fiber-glassing the exterior. Anyone have any knowledge?

PeterG
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Re: Transom motor mount holes, before or after fiberglass?

Postby PeterG » Wed Aug 23, 2017 12:24 pm

I don't have first hand knowledge, won't be at that point for quite some time, but I plan on drilling those at the time the motor is being fitted to the hull. Mount the motor, transfer the hole locations from the bracket to the transom, remove the motor and drill the holes.
Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

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hoodman
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Re: Transom motor mount holes, before or after fiberglass?

Postby hoodman » Thu Aug 24, 2017 6:32 am

There's really no way to know exactly where to drill the holes until you are ready to actually install the outboard. Go ahead and do your fiberglass first.

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Bill Edmundson
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Re: Transom motor mount holes, before or after fiberglass?

Postby Bill Edmundson » Thu Aug 24, 2017 8:02 am

It doesn't really matter when. You do need to seal inside the hole with epoxy or something like 3M5200. There seems to be a standard for the hole spacing, at least for medium to large engines.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

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BarnacleMike
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Re: Transom motor mount holes, before or after fiberglass?

Postby BarnacleMike » Thu Aug 24, 2017 9:36 am

I drilled mine after fiberglassing, as well as after I had used the boat for some time. I sealed the inner diameter of the holes with epoxy, and used stainless steel bolts, washers and lock nuts.

Here are a couple of links to how I did it on my boat, if it might be useful to you...

Drilling the holes: http://barnaclemikeboats.blogspot.com/2016/12/new-years-eve.html and,

Attaching the motor: http://barnaclemikeboats.blogspot.com/2017/02/bolting-motor-to-utility.html
-Michael

Built Utility "Perseverance" — completed Aug 2016
Currently building a Zip
My Boatbuilding Blog: http://barnaclemikeboats.blogspot.com/
My Website of Boat Photos: https://michaelsmaddox.wordpress.com

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Bill Edmundson
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Re: Transom motor mount holes, before or after fiberglass?

Postby Bill Edmundson » Thu Aug 24, 2017 10:01 am

I was mounting a 115 Yamaha. A bit bigger. I used my drill press to get a nice straight hole through a piece of 2x4. I located pilot holes in the transom with a smaller bit. Then used the 2x4 to make sure the holes were true.

Bill
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build


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