Welding Tips and Tricks

Hi all,

Just joined the forum but I've been looking at this site for a while now.

I went out fishing the other day and discovered a leak!! Not very good!! Lucky I've got a decent bilge pump!!

It's a crack along the seam between the keel (6mm allum.) and the hull (2mm allum.) about 100mm long.

I have 2 questions:

What is the best way to prep this old marine metal? And , Should I try and preheat the keel and use less amps (it's 6x50mm x 4m) or just crank the TIG right up to 200amps and push a big fat bead off the keel onto the thinner plate??

Hey mate
Older ally boats can be a bit tricky due to the fact the they will have absorbed salt into the metal a little and it will be right in through the crack. You will need to access the inside of the crack as well.
Clean both sides with tanker cleaner (acid) first, then I would wire brush the inside of the crack, go back to the outside and back chip the crack out. Yes pre-heating the keel section first will help, I don't keep a oxy set at my workshop due to the price of the gas, so I just crank the amps up to start with. I doubt you'll need 200 amps.
Whether you back chip the inside after and weld this as well will depend on the amount of peno and fusion you achived. Kinda your call, I don't as I usally get good peno, and I don't like to overweld ally on boats as it can have follow on effects.
Oh and I'd be looking for the reason why it cracked, usally trailer is set up wrong.

Good luck

Hi wojtech
ive done a few boats here lately, the last one i did was a real trainwreck i told the guy they make new boats everyday
i thought he was going to start crying. well any way what i wanted to tell you was to take your time and if you can back
the weld up with some brass or copper that will help!
good luck john
P.S clean thin clean again

You'll be chasing that crack from bow to stern if you don't drill-stop it first. You need to positively identify each end of the crack, center-punch it, and drill at least a 7mm hole straight through. I'd then suggest grinding 3/4 through along the entire crack and welding the first pass, then back-grinding 3/4 again for the next pass from the other side. On either pass, or both, you might back up the weld with a heat-sink like a slab of brass or copper (as suggested above). With the flexing a boat takes, I wouldn't use a filler harder than 4043, and might consider 3003 if the crack is as close to a hard member (the keel) as your description suggests.

Good luck,

Steve