Bertram 25 Front Engine Mount Bed - How to fasten the engine mount after removing rot.

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
chrisca
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Bertram 25 Front Engine Mount Bed - How to fasten the engine mount after removing rot.

Post by chrisca »

Hi Everyone,

Working on repowering a Bertram 25.

I have a rotted wood inside the front engine bed. The rotted wood is encapsulated in fiberglass and I plan to open the top and replace the wood with coosa and fiberglass that in.

My question is once I've completed the repair whats the best method of fastening the engine mounts to the engine bed. The original engine mounts were held down with lag screws. Can I use lag screws again or will coosa not hold up to the vibration?

Or should I bolt through with a large washer on the bottom? Access is really limited below the bed and I would have to cut access to thread the nuts on.

See picture below:

https://photos.app.goo.gl/4vUgPk3knyJxpPs97

fallguy1000
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Re: Bertram 25 Front Engine Mount Bed - How to fasten the engine mount after removing rot.

Post by fallguy1000 »

Coosa Bluewater should be fine, not the lower densities. You will need to make the engine bed thick enough to support the lag. So, you cannot drive a 3/8" bolt through 3/4" material, for example. And so, the bond of the coosa is also important. You will have a hard time drilling down the middle of an epoxy bond in two pieces of coosa as the bond will push the drill.

So, some planning of the drilling it important for success. A 3 layer layup of 3/4" coosa would afford you the ability to drill the middle layer without failing...
My boat build is here -------->

viewtopic.php?f=12&t=62495

chrisca
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Re: Bertram 25 Front Engine Mount Bed - How to fasten the engine mount after removing rot.

Post by chrisca »

Thanks

I just spoke to a coosa sales rep and he recomended to add a backing plate at the back. We're going to use a 1/4" stainless backing and a layer of coosa. Sandwich everytihng with fiberlgass.

Should be buletprrof

fallguy1000
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Re: Bertram 25 Front Engine Mount Bed - How to fasten the engine mount after removing rot.

Post by fallguy1000 »

Can you explain that better for others? What is the back?
My boat build is here -------->

viewtopic.php?f=12&t=62495

chrisca
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Re: Bertram 25 Front Engine Mount Bed - How to fasten the engine mount after removing rot.

Post by chrisca »

Add 1/4" stainless steel sheet below the coosa into which lag screws will be able to bite into. The 1/4 plate will have to be pilot drilled to get into it.

fallguy1000
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Re: Bertram 25 Front Engine Mount Bed - How to fasten the engine mount after removing rot.

Post by fallguy1000 »

chrisca wrote: Thu Aug 04, 2022 1:34 pm Add 1/4" stainless steel sheet below the coosa into which lag screws will be able to bite into. The 1/4 plate will have to be pilot drilled to get into it.
I'd probably use 1/4" stainless angle, bolt through glassed coosa on the sides and there is a tapped hole on top.
My boat build is here -------->

viewtopic.php?f=12&t=62495

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