Ideas for repairing cut down aluminum transom?

[reelfishin]

I picked up a super clean 16' aluminum boat today but a former owner apparently wanted it to be a 15" transom vs the original 20" transom and took a Sawzall to it. They cut out a trapezoid shaped section 5" down and about 18" across the top, leaving bare wood and metal exposed. I need it to be 20" again, not to mention that the cut hurts the strength of the transom on this boat as the top rail was a heavy gauge aluminum extrusion which is now cut.
I was thinking of making a new wood core, double epoxy coated 3/4" ply, bolting that back in place, and then getting a somewhat heavy gauge aluminum panel bent which will completely cover the whole top of the transom, plus about 6" down on the inside, and far enough down on the outside to cover the cut out panel and to also catch all of the transom wood panel bolts. I'd probably also paint the two panels pretty heavy in between as well as maybe a coat of epoxy to keep water or salt out. I also have to deal with a bolted in knee brace which was originally riveted but is now bolted in with bolts that are about rusted away completely. The lower rivet flanges are gone from the brace, so I may just get that welded to a piece of 3/16" plate and then bolt or rivet it back in place. Then I need to deal with the four 5/16" holes drilled thought the bottom of the boat. The holes are drilled just outside of the keel strip, making sealing them with a rivet impossible. I'm thinking that they may need to be welded closed?

 

[Bondo]

Re: Ideas for repairing cut down aluminum transom?

and then getting a somewhat heavy gauge aluminum panel bent which

Ayuh,.... Mic up the aluminum that's there.... Starcrafts use .063",... I wouldn't go thicker than .090"...
Too thick will create "Hard" spots,...
Ditto the knee brace...

Thicker isn't always Better...

 

[erikgreen]

Re: Ideas for repairing cut down aluminum transom?

You know, your plan sounds pretty good for the transom.

But, since you're thinking of getting it welded anyway, I want to put in that the "right" way to do it is the obvious way... get a piece of aluminum alloy the same type as the hull (marine 5052 or something) and have it welded so it's even with the transom height you want and butted up against the existing plate. Then have the welder sister on another piece of to overlap the joint on the inside.

Likewise weld or replace the extrusion at the top, then install your wood.

For the other stuff, welding would seal the holes well... the tough part will be getting the metal clean enough to weld properly, which is more or less the welder's problem

Erik

 

[reelfishin]

Re: Ideas for repairing cut down aluminum transom?

........ For the other stuff, welding would seal the holes well... the tough part will be getting the metal clean enough to weld properly, which is more or less the welder's problem

Erik

This has always been the issue when trying to weld an old hull, especially one that may have some contamination. If the rest of the boat wasn't so perfect, I'd not bother. My concern is not being able to find a suitable top cap or extruded panel, if I can find a new top cap just like the original, I won't need to do anything but have the patch welded in place. I can add an outside wooden transom pad to cover the seam, and the new wood transom panel will no doubt take the load. The transom aluminum is thick, thicker than any other boat I've seen. It mics out at .096". The whole hull is like that.

My thought is that if I can't find a new transom extrusion, I may be better off making a new cap, running the plywood all the way to the top, flush with the top of the transom, and having a "U" shaped transom cap bent up with a 1.6" I.D. to cap the entire transom, going 4 to 6" down in the inside to catch the outboard clamps, and down the outside enough to form an outer motor plate. I also thought about welding on a thicker motor plate just for added protected vs. using a wood panel on the outside.
If I build the transom as a three piece sandwich with glass mat and epoxy, it will no doubt be stronger than anything that was there from the factory, plus it would hide and effectively repair the cutout.

Another idea that has crossed my mind is to do the above repair and mount an adjustable jack plate, which will allow me to still run either length shaft motor. The plan at first was just to get the transom set up again to run my 40hp Mercury, but it would be nice to still be able to run a smaller engine in HP restricted water.