Welding Tips and Tricks

OK fellas, here it is. Looks very nasty. I'm not even feeling like doing it. What do you recon? I have 4043 and 5356. I have the broken piece (in one piece). Can't see any other cracks. Apparently been broken since new about 35 years ago.

WOW, Coldman. You can certainly get into some interesting stuff. I have never gotten into cast aluminum..YET, but have watched several videos by Jody (wwtt) and Jason (fabricator) and noticed that patience is very necessary for the job. It's more like brazing than welding due to the crap in the casting.
Keep us posted on this one and best of luck. OH, is this a part of another boat or something else?

In my recent travels, I was able to salvage a two tonne winch, gearbox and motor out of a boat shed that was about to be demolished. Nobody wanted or cared to remove it and I was invited to knock myself out. I brought it back with me and it now occupies space in my shop on the parts shelf. I don't have a use for it, just don't like to see good machinery go by wrecking ball. Thought I might tidy it up. If I mount it all on a base I could probably sell it.

I would go with 5356. Clean the best you can. A deburring tool is good to dig down a bit. I would make my groove on the back side and put most of my weld underneath. Good luck.


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I don't know if you will have any luck welding the old piece on. What would do is build it up with 4041 or aluminum bronze (whichever adheres the best I guess?) and grind it back into shape and re drill the hole.

Louie1961 wrote:I don't know if you will have any luck welding the old piece on. What would do is build it up with 4041 or aluminum bronze (whichever adheres the best I guess?) and grind it back into shape and re drill the hole.

I like your idea better. It's not a huge piece to build out. 5356 is my go to because i believe it's more ductile than 4041. Never used aluminum bronze but that sounds like a good option. I assume you can keep your temperature lower which is good for keeping crap from coming up.

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Ah - more quality boat work - seems like a theme starting here ! my 2cents - don't try to weld it unless you just pile on spool gun poop & shape it back - Tig is just going to boil & spit till there is nothing left - if it were me I'd make a copper " dam " around the outside shape & fill with " HTS2000 " low temp rod & a torch - that stuff sticks to almost anything & will be stronger than the original broken ear.

I would look at 4047 rod. It is high silicon, so it wets well. Melts at a lower temp, so you aren't pulling up so much crap from the casting. I have used it on cast aluminum before switching to 4943. I prefer the 4943, but I've never used it on cast as ugly as what is in the photo.

I've done several cast aluminum repairs like this one.

Just be sure to clean it with a die grinder, only use enough power to puddle it, weld it up

Just welding and grinding to shape works too.

Either way, a good file finishes it off nice and straight after rough grinding.

I was trapped at the shop today waiting on a vacuum pump to pull down the AC system on a motorhome. Thought I would try a head to head comparison between 4043, 4047 and 4943 on cast aluminum, while I was waiting.
Went to my recycling pile, and found a back cover from a GM coolant pump. Oil and antifreeze soaked, with a nice patina of oxides. Just right for the test I had in mind. Broke it in half with a vise and big hammer. Found it to be stiffer, and more brittle than typical aluminum cast. A quick pass with a Scotchbrite pad, and a bit of bevel with a sanding disk. No further cleaning was done to keep the results meaningful for crappy casting.

I ran a bead with each of the 3 rods. The 4043 was the hardest to deal with. It had a sluggish puddle, and required the most heat to get it to flow. It had a number of tiny spikes on the surface and some porosity.
The 4047 'flowed in' with a lot less heat. It also had a better surface finish. The 4943 was the easiest to use. It took a little more heat than the 4047, but it 'wet in' nicer. Surface finish was similar to the 4047.
Did the hammer and vise thing again. It was a bit ductile before breaking this time. Break was along the edge of the 4943, and into the 4043. It did separate a small amount of the 4047.
What I learned, if heat input is critical, use 4047. Otherwise, I will be using the 4943.

Thanks for that. I was toying with getting some 4047 next time I went to my LWS before I made my post. Definitely will now. Never been a fan of 4043, just happened to have a few left over from a previous cast repair. Ordered some replacement outer shields for my Optrel hood, should be in today or tomorrow, will pick some 4047 up then. Not rushing into this repair as it's for myself and will wait till it won't interfere with work work. Also to get full access to the joint I have to remove the front cover/bearing housing, so I plan to give the motor a birthday at the same time and change out the bearings. Already picked up an aluminium burr to be ready for clean up.

If you have a problem with a lot of crap bleeding out of the cast, then the 4047 will allow you to keep the heat input to a minimum. I'm starting to think 4043 is only good for practice.
The 4943 is quickly becoming my favorite. It does cost more than 4043, but at least it isn't Hastelloy.