Using Aluminum plate for a transom instead of wood

[Jlew]

I have a Lund boat just shy of 20 feet long with a 115 horse motor.
The boat has been a project of mine for a few years now and my transom was in decent shape when I replaced the motor this year year however I'm looking to replace it with an aluminum plate I work in a metal shop where I have access to the tooling required to cut out such a piece, has anyone done anything like this?

 

[airshot]

I have often wondered why the mfgrs havent done this before now??

 

[Jlew]

I have often wondered why the mfgrs havent done this before now??

I don't know either but maybe it's a structural thing maybe the aluminum could crack and spit under the torque where as wood can flex I have no idea so if anyone has ever heard of someone doing this any input would be awesome

 

[jbcurt00]

Wood dampens vibration and gives some grip for the exterior 1/2 of the transom clamp assembly

Many (most?) Starcrafts documented here have swapped to an aluminum plate.

Doesn't NEED to be 1/2in+ thick like most wood ones

 

[Chris1956]

My fiberglass speedboat has a 3/8" piece of aluminum bolted to the wooden cored transom. It gives added strength. However, if that was the only transom, it might bend under stress. The plywood core of the transom is better for shock absorption.

Not sure what thickness of plate you would need. Perhaps weld some ribs onto a 3/8" thick plate for added strength?

Jackplates for 150HP motors are 3/8" aluminum, however, they are just the size of the transom clamp, which makes them rigid.

You might check out bolt on brackets for boats. They are made to hold larger motors. See what they are made of.

 

[airshot]

I would think a 1/2" piece of aluminum then add a one inch piece of plywood that could easily be replaced would work well. The alum would give strength and the wood for vibration and lateral strength. Just design it so the wood could be replaced easily, unlike the factory designers do.

 

[jbcurt00]

@airshot on an aluminum boat, the wood pad in question is on the outside of the hull
A 1/2in aluminum plate plus 1in plywood would make the transom 3in thick w a 1.5in wooden transom on the inside of the boat.

 

[airshot]

@airshot on an aluminum boat, the wood pad in question is on the outside of the hull
A 1/2in aluminum plate plus 1in plywood would make the transom 3in thick w a 1.5in wooden transom on the inside of the boat.

Guess I assumed wrong, over all you need about 1 1/2" on total thickness of the transom

 

[Jlew]

Thanks for all the input everyone!