Anything special to know about welding up an aluminum pontoon?

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Boss sent me a picture a few minutes ago asking if I could weld up a gash in a boat pontoon. I don't know anything at all about what alloy is used to make a pontoon. I know we have some 5356 filler and the usual 4000 something filler(drawing a blank on exactly what it is). TIG process.Gash looks to be maybe 3-5 inches long and maybe 3/4" across at the widest point, so I'm thinking it needs to be patched rather than trying to fill it(his idea, not mine).
Reply:Good 👍 luck. I can help with steel and I would use mig.I seen done in aluminum and they used a spool gun and a fine mig wire.Dave

Originally Posted by machinisttx

Boss sent me a picture a few minutes ago asking if I could weld up a gash in a boat pontoon. I don't know anything at all about what alloy is used to make a pontoon. I know we have some 5356 filler and the usual 4000 something filler(drawing a blank on exactly what it is). TIG process.Gash looks to be maybe 3-5 inches long and maybe 3/4" across at the widest point, so I'm thinking it needs to be patched rather than trying to fill it(his idea, not mine).
Reply:The below blurb was found on a Miller welding forum, hope it helps.Almost all "pontoon" boats made for recreational use in the US are made out of 6061T-6 Aluminum in .063" (approximately 15 gauge). The two exceptions to this are Bentley Pontoons, which are made with .080 extruded, and the Trimarans (3-tube) made by Bennington, which are a full 1/4" (.125) thick H-34 aluminum. H-34 and T-6 are similar in that they're both heat-treated and both anodized, but the base material for H-34 is slightly softer (hence the thicker material).
Reply:Tig it with 5356 and straight argon. Twas me I would not make a patch. I would just knit the hole closed.Weld like a "WELDOR", not a wel-"DERR"

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Reply:Thanks for the info guys. Area might be smaller than it appears in the picture. I'm reasonably certain I could knit it back together, but I suspect he's gonna lowball the price and be back there asking about it every ten minutes...like me stopping to answer questions helps it get done faster.
Reply:Never done it myself but this question has arisen a few times in recent years, you might be able to find these threads. From what I remember, repair weld and patch weld both have been done successfully. The biggest problem was contamination and for this reason patching with mig was fastest. Depends on the extent of the damage I suppose. 5356 was the go to filler.
Reply:Water goes on the outside.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:I might pull a piece in behind it for a backup then plug it full.www.urkafarms.com
Reply:i cant remember if those 'toons are foam filled??lincoln 125spdayton 250 ac/dcmiller 211 w/spool gunahp  200 sx tiglotos ltp5000dkubota b3200 FEL BHof course duramax diesel
Reply:I have repaired pontoons before. So far I have never encountered any foam filled ones. My experience has been that over all, it is easier to make a nice-looking patch to tig weld over the damaged area instead of trying to knit it shut. Situations vary, of course. One of the difficulties one can encounter from welding a split area is the difficulty of cleaning the backside of the aluminum. It seems like it is easy to pull in contamination from the backside of that edge. And the finished work still may show a crease in the damaged area. A neat patch ends up getting my vote. However, I didn't see any picture of the problem. There may be times I would just weld it without a patch. I also use 5356 for pontoon repair.
Reply:

Originally Posted by El Greco

The below blurb was found on a Miller welding forum, hope it helps.Almost all "pontoon" boats made for recreational use in the US are made out of 6061T-6 Aluminum in .063" (approximately 15 gauge). The two exceptions to this are Bentley Pontoons, which are made with .080 extruded, and the Trimarans (3-tube) made by Bennington, which are a full 1/4" (.125) thick .
Reply:Be sure and unscrew the drain plug so that pressure wont' build up while welding!
Reply:The other issue to consider is liability if something fails and it sinks. It doesn't need to be your fault once the lawyers are involved. I run a fully insured commercial fab/welding shop and I rarely, if ever, touch boats.