Repairing Old Aluminum Boat

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Hello Weldingweb. Sincere thanks from an amateur for all the help and advice in the past. I really appreciate the insights and knowledge on this forum. I have a friend with mental issues and during covid lockdown he started to collapse so I bought this old boat (1970 Lowepro) and trailer for $400 and dragged him out to work on it. It is a 16" boat which to us is far superior to smaller ones. Anyway the last owner changed it from a 20" transom to a 15" transom by taking a sawzall to the transom (idiot, who does that?). I need to restore to 20" by fixing the hole. It does not look like a bad repair. The boat is 0.063" 5052-H32 plate. I bought a piece of plate and my idea was that it needed to be bent with the channel on top, fit into the hole, and welded in. I also bought some marine plywood and will laminate it in with epoxy after the repair to make a strong and waterproof transom. I can bend the plate but I have never welded aluminum, equipment not in budget now. I was going to look for a welder in this area (Golden BC Canada) who would weld it for me. But my neighbour who is an amateur machinist told me that if I weld this thin plate it will crack around the weld. He suggested putting a larger patch over the missing piece and welding that around the perimeter, which doesn't make sense to me as it seems it would add no strength and would look like crap. The strength in this repaired transom will be the lamination of aluminum plate and epoxied marine plywood. My question is: can I weld a patch in the missing cut out, or will the repair crack? Any other suggestions for procedures etc. would be greatly appreciated. Again, sincere thanks to everyone who posts here, you may not know but you have helped a lot of us through some hard mental times, hope you have a great day      






Reply:If you can clean the metal and get past any corrosion, you'll get a nice weld, I don't see why it would crack, there's plenty of welded aluminum boats.Sent from my fab shop using a mig welder and a grinder

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Reply:If it was me I'd bend up a piece of aluminum like this, overlap it quite a bit, maybe use rivets to hold it all tight, then weld it out, inside and out, then drill the rivets out and plug the holes,If you can do it without drilling and putting rivets in it would be better, maybe you can clamp it somehow.

And it goes without saying that it needs to be extremely clean, maybe use a stainless wire brush on an angle grinder, get it really really clean. If you do all the prep work and have it all clean and ready to weld and clamped up, you'll save yourself some money, that way whoever you hire to do it can just start welding. Sent from my fab shop using a mig welder and a grinderLast edited by MetalMan23; 16 Hours Ago at 10:56 AM.

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Reply:Will the top of the transom be flat when you restore it to 20” or willit still be lower where the motor mounts.I’d personally opt for a glue and screw rather than welding.Replace whole wooden piece and bend aluminum piece tocover top and outside of transom.Miller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:

Originally Posted by jpump5

Will the top of the transom be flat when you restore it to 20” or willit still be lower where the motor mounts.I’d personally opt for a glue and screw rather than welding.Replace whole wooden piece and bend aluminum piece tocover top and outside of transom.
Reply:I’d personally opt for a glue and screw rather than welding.Replace whole wooden piece and bend aluminum piece tocover top and outside of transom.
Reply:I concur with the "why not replace it with wood" sentiment. Especially if there's no experience with welding Aluminum things can get out of hand and you end up with a warped piece of aluminum that also leaks. Worst case scenario is it lets water in somewhere you can't see it until there's a big problem.The current aluminum looks like it has some convenient holes in it already, it'd be a pretty easy job to replace with wood I'd think. Easier than trying to fit, clean and weld some plate in there at least.If welding is absolutely what you want I'd start by seeing how deep that corrosion is/how thick the material is after you clean up a spot. You'll want to get everything to shiny clean metal if you want a weld that holds and doesn't leak. I'd think a buttweld to replace the missing section would be preferable to a lap weld since it'd reduce the risks of creating a space for water to seep in where you can't see it. That would mean fitting a replacement plate into the missing area, ideally with minimal gaps. You'd need to clamp and hold it all flush while you get it tacked and probably welded. Probably won't be straight or flat when you're done either. You'll need to weld up and horizontal which can be tricky for a new welder.
Reply:He said he doesn't have budget for buying welding equipment, so I'm assuming he'll be hiring someoneI do like the idea of bending a piece over, sealing with 3m 5200, and then screwing it into transom with stainless screws, that would also work.Sent from my fab shop using a mig welder and a grinder

http://www.philswelding.com
Reply:

Originally Posted by MetalMan23

He said he doesn't have budget for buying welding equipment, so I'm assuming he'll be hiring someoneI do like the idea of bending a piece over, sealing with 3m 5200, and then screwing it into transom with stainless screws, that would also work.Sent from my fab shop using a mig welder and a grinder
Reply:Looks like a fun project, like mentioned early I'd have some aluminum bent to fit and weld it up.  The aluminum needs to be really clean. dont grind on it just brush it with brass bush until you remove all the oxides.We've done so much, for so long, with so little. Were now qualified to do anything with nothing !
Reply:

Originally Posted by duramax-rob

the strength of transom is in wood.  replace entire wood transom and just attach al. to keep from leaking.
Reply:In 2017 I reworked the transom of a 1960’s 14’ Duracraft ditching the double 3/4 plywood for aluminum rectangular tubing and plate. Used the original bolt holes and went thru both the tubing and plate. I ran it with 1968 Johnson 9.5 and it worked great. Here are pictures of the tubing and it installed in the boat before the piece of plate was placed over it. On the floor of the boat is the knee I cut in half and later sistered with two pieces of aluminum, bolting it back together.


Last edited by El Greco; 4 Hours Ago at 11:42 PM.
Reply:Thanks for taking the time to make and post this. Makes complete sense, along with the other comments regarding epoxy and laminations. This is what I am going to do. Thanks again! John

Originally Posted by MetalMan23

If it was me I'd bend up a piece of aluminum like this, overlap it quite a bit, maybe use rivets to hold it all tight, then weld it out, inside and out, then drill the rivets out and plug the holes,If you can do it without drilling and putting rivets in it would be better, maybe you can clamp it somehow.

And it goes without saying that it needs to be extremely clean, maybe use a stainless wire brush on an angle grinder, get it really really clean. If you do all the prep work and have it all clean and ready to weld and clamped up, you'll save yourself some money, that way whoever you hire to do it can just start welding. Sent from my fab shop using a mig welder and a grinder
Reply:Very nice work, thanks for this!