[Backyardmech]

Just looking to see if anyone here has expérience in welding aluminum boat hulls..I have a 16.5 ft fishing boat with 2 small cracks at the bottom from at the bow. Leaking water bad whwn I had it in the water..I have a lincoln 180 with a 100 spool gun. IVe done a fare bit of aluminum welding at work on our aluminum molds..but this will be my first boat..thickniss is 100 gauge. Any tips would be appreciated.

[Oilman]

Never welded an aluminum boat, but I would expect you might want to grind out the crack to eliminate any oxidation in the crack and make sure the surrounding surface is really clean and free of oxidation. Wipe it down good with acetone before welding. I know with welding steels that crack migration is an issue so we ground out cracks, following them until they were not discernible and then drilled out the ends. I would think about getting some similar thickness aluminum to practice on and make sure the machine setting were correct. There are dye penetrants to show cracks.

Another thought is to preheat and maybe post heat the area a bit to to help normalize any stress.

Anyone else?

[Otto Nobedder]

Good recommendations.

On thin aluminum, I'll often grind through like this, then back up the gap with a piece of clean steel or stainless when welding, so I don't risk drip-out from getting too hot too fast.

Steve

[Backyardmech]

Well I started on it today..grinded out the crack area and cleaned it up nice. But after closer inspection I found that the crack started because of the aluminum is woren down there from beaching the boat over the years..so the it's very thin there. I had to be very careful as I kept burning holes in the area around the crack. Managed to build it up and fill it in, now I'm worried about other areas in that part of the bow being thin and weak now. Thinking of taking your advice steve and add a plate to reinforce that area..

[Backyardmech]

I'm also starting to think i might need to fill in from the other side to? Any thoughts on that? Would mean pulling the floor out...but i want this done right..

[Poland308]

Since its worn thin and you will be useing a spool gun I think you will make it a lot easier on your self if you pull the floor and use a backer plate on the back side of the crack. That way you can crank up the spool gun and burn through from the front if you get full penetration and it welds to the plate even better.

[Otto Nobedder]

... Thinking of taking your advice steve and add a plate to reinforce that area..

That is not what I meant... The clean steel or stainless is simply there to contain your weldment, so it doesn't drip out. It won't stick, and doesn't stay. I didn't realize you didn't have access to both sides.

Frankly, if you're looking at beaching wear, I think I'd fab a skid plate that fit and covered the worn area, and rivet it on with a high-grade marine adhesive to waterproof it. Welding would not be my first choice, given this new information.

Steve S

[RamboBaby]

What filler are you using? I believe marine applications require 5356. Otherwise the weld will corrode rapidly.

[Artie F. Emm]

Not to hijack the thread, but...

thickniss is 100 gauge.

I had to look up 100 gauge, and the source I found said the equivalent is 0.001". Can that be right? That's 1/10th as thick as aluminum foil.

[Backyardmech]

Not to hijack the thread, but...

thickniss is 100 gauge.

I had to look up 100 gauge, and the source I found said the equivalent is 0.001". Can that be right? That's 1/10th as thick as aluminum foil.

Sorry, my mistake...i missed the decimal point. .100 gauge..that looks better. Lol

[Otto Nobedder]

Frankly, I'd think it's 10 gauge... 0.135". A far more appropriate thickness for a boat hull.

Steve S

[Backyardmech]

Frankly, I'd think it's 10 gauge... 0.135". A far more appropriate thickness for a boat hull.

Steve S

I still have our original owners guide, said hull was made with .100 gauge aluminum..boat is a 1997 Legend 16.5 ft boat. Thats my best info to go on...boat was given to me be by my dad.

[Backyardmech]

What filler are you using? I believe marine applications require 5356. Otherwise the weld will corrode rapidly.

Using 4043...yes i now realize its not the right filler..but it came with the gun. And im still learning this aluminum welding thing. Crap...way différent then reg steel mig or fluxcore..

[RamboBaby]

Make sure that you check it good before you take it out for a ride. I've seen a lot of leaky aluminum mig welds come into the shop in the past. Tig is a much better process when you need something sealed up tight.

[Tommy2069]

i always grinded the crack out then drilled a hole at each end just to make sure the crack stops there.