Aluminum Plate for Transom

[WillyGeeTX]

Hey guys I believe this is my first post. I have just bought a mint 2010 Alumacraft 1448. Mint as in only ever had a trolling motor on it, pretty much garage kept. I am looking at a 15 hp Tohatsu with 17 hours on it and it is reasonably priced. I would like to beef up the transom with two pieces of aluminum plate- T-6 1/4". One on the inside and one on the outside. I am asking:
1. what is the outside dimension of the motor mount between brackets (so I don't put a bolt there)? I have a diagram from the manual that shows about 194 mm which converts to 7.6 inches is that about right?
2. Is there any other reasonably priced material that would work instead of T6 aluminum? I have watched quite of few videos of bonding 3/4" plywood together and fiberglassing but I am looking for the quickest way out.
Thank you for your assistance.
Bill

 

[1960 yellowboat]

If the plates are just attached to the current transom, they still depend on that thin piece of aluminum for strenght
They would have to be, in my opinion, attached to the hull itself.

 

[LDUBS]

If the plates are for cosmetic purposes then maybe use one of the rubber transom pads. If the transom is sound, but beefing it up brings peace of mind, then I would also go with aluminum over plywood because it will be cleaner, less maintenance, and less chance of failure. And, I personally would consider 1/8" thickness (just my opinion). Adding plates to address an unsound transom might not be the best idea, but it sounds like you don't have that problem.

The dimensions provided in your manual should be good. I assume your transom is somewhere from 1" to 1 1/2" thick. As long as your mounting bracket will handle a transom thickness ranging from 1 1/2" to 2", you are good adding the two 1/4" plates.

 

[eeshaw]

1/4 inch is big time overkill, use 1/8 inch and it'll be fine and you'll save half the weight of the 1/4 inch.

 

[airshot]

If your motor is a clamp on mount, consider plywood on the inside to give the clamps something to bite on..Saw more than one motor slip off a metal transom with no wood to bite on. If a bolt on engine mount then go for the all metal, but as another poster mentioned, adding a half inch of aluminum is really overkill. !!!

 

[Danman]

Not sure your reason for beefing up . If intent is to provide a clamping surface as not to damage or compress the original skin. The go buy a sheet of king starboard. Or go to Walmart and buy a Teflon cutting board Same effect

 

[eeshaw]

If you have a clamp on motor you can always add bolts to hold it to the transom also.

 

[Danman]

Google “transom plate”. “ then Images”……,Hundreds of photos, ideas and dozens of already available commercial products,

 

[Weldorthemagnificent]

I do this too, it helps spread out the forces. I use 5000 series aluminum if I can get it, currently using 5083 because I had a chunk leftover, 3003 is fine as well. I work at.a welding/machine shop so picking scraps up on the cheap is easy for me. I wouldn't stress over what type of aluminum. Visit your local welding shop and see what they have kicking around.

 

[thill]

If your motor is a clamp on mount, consider plywood on the inside to give the clamps something to bite on..Saw more than one motor slip off a metal transom with no wood to bite on. If a bolt on engine mount then go for the all metal, but as another poster mentioned, adding a half inch of aluminum is really overkill. !!!

Many years ago, I had a motor slide off a transom during a turn and plunge to the bottom of the Bay in 45' of water. Definitely use wood on the inside if it's a clamp-on motor. Consider also using keeper bolts.

If you want aluminum on the outside, that's okay, it doesn't weigh that much, and it will help spread the load. Instead of wood, my Princecraft has a transom build from stacked 2" Schedule 40 square pipe and 1/4" aluminum plate. It may be overkill, but it is crazy-strong. That transom will never have an issue.

But just remember that weight is a factor on a 1448. You may want to move your batteries and fuel tank forward if your new 4-stoke is heavier than you think. I water tested a 15HP Mercury 4-stroke, and it was 2 lbs. heavier than the 30 hp Johnson that it left here with.