Transom support

[Milton.Audas]

Hi guys. One of my seemingly never-ending upgrade list items is to install a support bracket or plate inside the transom (ie in the port aft locker on the 'old style'). Has anyone got any commercially available options. Vertical hole spacing on my bracket is only about 5" - 7". Horizontal about 5". Related question : are these plates mounted vertically or horizontally ?
I've seen a few advertised on WM and others, but most state 12-13" hole spacing. eg. T-H MARINE Transom Support Plate | West Marine
Any ideas, links ?

Cheers,
Milton

 

[Dave Groshong]

I don't know of a commercially available one. I would use a piece of aluminum, or epoxy coat a piece of 3/4 inch marine plywood and use large fender washers.

 

[rpludwig]

hefty aluminum L angle from big box installed vertically works, or what Dave sez, I simply used jumbo galv fender washers....https://www.mcmaster.com/galvanized-steel-washers

 

[AaronD]

Support rails are normally mounted vertically. As @rpludwig said, angle aluminum or stainless. CD's version is stainless, and pre-drilled for the standard Garhauer mount (the holes might or might not fit your motor mount's spacing - call CD to confirm; they're very helpful). Stingy Sailor used aluminum (scroll down in that page for a picture). I wanted to avoid bimetallic corrosion between stainless fasteners and aluminum rails, so I went with the stainless. And, being somewhat paranoid, I added a big G10 plate as well. Hope that helps a little.

 

[pclarksurf]

On the plywood front: relatively easy to work up a 3/4 marine ply backer-- coated in epoxy and bonded to the inside of the transom:

Ideal for motor mount and gudgeons.

 

[Milton.Audas]

Thanks guys. Good advice. I am sure that the transom was initially designed to withstand the rigours and mechanical forces of that motor attached to the blunt end of the boat, especially when in the 'down' position and extended further away from the transom. But over time, I suspect that the wood core is not quite as it was when new so trying to avoid a catastrophic failure. Any means to distribute the load and avoid higher stress points such as the 4 mounting bolts is an improvement. I like the angle alumINIUM approach, as well as the backing plate. I have marine ply so maybe both, if i can find high tensile bolts long enough. Cheers !! Hopefully we can get boats in the water and be able (allowed) to play soon !! But better we stay away and be healthy, to play again some day with luck.

 

[rpludwig]

Milton....whatever you decide, suggest you work with McMaster-Carr for "high tensile bolts"....their service is great and prices are fair enough....big box bolts, even SS are not a good option...

 

[Milton.Audas]

Milton....whatever you decide, suggest you work with McMaster-Carr for "high tensile bolts"....their service is great and prices are fair enough....big box bolts, even SS are not a good option...

Agree. we have an account with MMC

 

[AaronD]

... high tensile bolts...

The standard for corrosion resistance is 316 stainless, available at McMaster and boltdepot.com. (Judging by your location, I'm guessing you're not in salt water, so maybe corrosion resistance doesn't matter as much to you, but maybe it'll help someone). Yes, 316 gives up some strength for that corrosion resistance (vs 304 SS or non-SS bolts). @thinwater lists some specs for 316 on his blog. IIRC, my motor mount used 4x 3/8" bolts, which spec to a working load of 1200+ lbs each. That seems plenty for this application.

 

[pclarksurf]

thumbs up for Bolt Depot as well-- have used both. Bolt Depot has excellent supply in various grades you don't often find elsewhere.

 

[Gene Neill]

12" x 12" x 1/2" structural fiberglass plate, for $34.27?