is there a secret to welding cast aluminum?

bob johnson · Mar 23, 2009

I got my motor apart and the lower unit is bare. the case has some pitting on it and I was going to try and fill it in with our TIG machine before i painted it.

but it just dont want to puddle.....

I also want to straighten the skeg which is slightly bent and a small cip in it..

so If you got a tip let me know please.

bob

jbjennings · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

You're surely a better welder than me, but I've found just by watching others that the aluminum has to be flawlessly clean and brushed with a stainless steel brush before welding. ALso, it has to be shielded with argon. (which a TIG welder would be).
Just a thought,
JBJ

R.Johnson · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

If you have never welded aluminum, that would be a very exspensive part to learn on. Those cases can be welded, but we always sent them out to a welding shop that had experience with this type of work.

bob johnson · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

I have welded aluminum for a dozen years and can do a decent job....I sandblasted the case and tried to even file it to clean it up....but the pits dont clean up....they are too deep...

I got some puddles to stick but it was a lot of work....

if it was really solid. I'd have less worry and just go to town....but i dont want the inside to cave in on me, sinking all that heat into it waiting for a puddle.

i got plenty of gas in the weld area....it looks like it wants to sag before it puddles...............

maybe because it is such a huge heat sink that the puddle galzes over so fast.

still receptive to any tips

PS: the OMC light blue paint is really hard to find!!
i went to 2 west marines and found one can and then to another large marine place locally and couldnt find any more.

one guy said he thinks the company went out of business

the can i have is made by MOELLER

thanks

bob

R.Johnson · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

Bob: As long as there are just pits, and you are going to paint the case, could you fill them with marine-tex, or J-B weld? I am not a welder by any means, so I can't help you there.

bob johnson · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

R.Johnson said:
Bob: As long as there are just pits, and you are going to paint the case, could you fill them with marine-tex, or J-B weld? I am not a welder by any means, so I can't help you there.

I would if I had the confidence the repair would stay put and not peel and take my paint with it..and be back to an ugly LU.

because it is only consmetic trying to smooth out the pits.

straightening the skeg is different.

is marine tex, like a bondo? is it sandable

bob

jbjennings · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

Dang, Bob!
You're risking warping/destroying the case just for cosmetic purposes?!!!
And I thought I was ridiculous!!!!

YOu're going to get some really good ones on this!

JBJ

Really, though, I think that marine tex stuff would stay if you scuffed it up with no problem. At least, I'd try it before the welding.....
JMO,
JBJ

bullbat · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

if ur worried about looks so much maybe you should but a new one. i wouldnt risk messin up a perfectly good foot just for a few pits that could be fix other ways and still look decent my engine may not be the prettiest but she purrs like a kittin and gets me where i wanna go

bob johnson · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

well at least I had enough sense to not go to town on it, because I know aluminum gets soft over a large area sometimes and can sag!

and i was worried about it sagging in and changing my bore for the shift housing!

Ill try some marine tex...and leave it at that.

bob

5150abf · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

Ya, if it doesn't leak clean it up really well and use the JB or Marintex, you will never get the pits clean enough to weld.

The lowers are cast and while it is good aluminum it can be a real challenge to weld right especially as you said becaus eit is so thick.

You do stand a very good chance of warping it if you keep welding on it.

When I do my props I have found you want just enough heat to melt it, too much and you get alot of pourosity, but again the lower is such a heat sink I don't know if you can do it without warping, I have welded a new skeg on but that is alot thinner there.

For the record I have been an aluminum TIG/MIG welder for 22 years and if it were mine I would JB weld if it didn't leak and get a new anode.

sebago_kid · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

Not too sure on welding cast Alum... but cast iron and steel, you have to beat on the welds with a hammer while still cherry red to re-align the molecules of the metal. If not, you might as well be using JB Weld. It'll break out. Not sure if Alum is the same... beating on the welds keeps them somewhat maleable.

kenmyfam · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

If it's cosmetic only then use the filler. If you insist on welding it get some etching fluid to clean the pit marks that you can not clean otherwise. It is acidic and will etch the pitted surfaces clean before you weld. Enough shielding gas (argon) and the correct tig tip (not to a sharp point) like you do with tool steel welding and you should be O.K. without melting your motor. Make certain the aluminum rods you are using are not old as they do not weld in difficult situations when they are older.

bob johnson · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

kenmyfam said:
If it's cosmetic only then use the filler. If you insist on welding it get some etching fluid to clean the pit marks that you can not clean otherwise. It is acidic and will etch the pitted surfaces clean before you weld. Enough shielding gas (argon) and the correct tig tip (not to a sharp point) like you do with tool steel welding and you should be O.K. without melting your motor. Make certain the aluminum rods you are using are not old as they do not weld in difficult situations when they are older.

yeah I was using a 3/32nd dia pure tungston rod with a full radius.

I had the heat up close to 200 amps i guess....I had sandblasted the whole thing good...there wasnt any coorosion in the old pits...but it wasnt shinny aluminum like youd want...it was sandblasted.

every once in a while I could puddle a little but there was so much heat in there it would cool as i tried to touch my rod to the puddle.... I couldnt get the rod to go into a liquid puddle......yu know that grey haze that glazes over your heated zone, that tells you it is about to cave in!! ha ha

i saw that and got worried....truth is the pits i was trying to weld were not over a bore actually..they were over the last opening where the shift rod goes down through.

anyway. I wont try welding it any more..ill probably make more work for myself.

I wll try to find some marinetex..it should stick to freshly sand blasted surfaces.

I think my bigger issue might be the pitting on the drive shaft bearing dia...trying to figure how i want to deal with that with out buying a $500 plus drive shaft or buying a used one for $250 and getting the same problem i have now!!

bob

Woodstock60 · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

I just redid one of my lower units that was pitted bad from the salty brine, I tried several things until I said screw it and ground it all down with a bench grinder. There was plenty of meat left after grinding, then I used an orbital sander with different grits to get a nice finish. I primed with acid etch primer and spray painted with Marine outboard lacquer. and although it wasn't perfect it was damn good.

http://i569.photobucket.com/albums/ss133/squid12121/LUrepainted.jpg

jay_merrill · Mar 23, 2009

Re: is there a secret to welding cast aluminum?

I used to do a fair amount of TIG welding "back in the day," but never tried cast aluminum. My understanding, however, is that part of the difficulty is because of all the voids in the material. On one hand, you have a thick piece of aluminum, which would indicated a higher "heat setting," but you also have a material that isn't solid, so burn through occurs easily.

I absolutely agree that trying to weld something that is hard to weld in the first place, isn't worth the effort when the reason for doing so is merey cosmetic.

As for the paint, try this business:

http://www.towerpaint.com/

I had a similar problem in regard to matching paint color once and bought paint from them. They will ask you to send a part to color match and will return it with your paint. They will also fill one or more standard aerosol cans with your custom paint, at a very reasonable price. I was very happy with the product and service from Tower Paint.

kenmyfam · Mar 24, 2009

Re: is there a secret to welding cast aluminum?

bob johnson said:
yeah I was using a 3/32nd dia pure tungston rod with a full radius.

I had the heat up close to 200 amps i guess....I had sandblasted the whole thing good...there wasnt any coorosion in the old pits...but it wasnt shinny aluminum like youd want...it was sandblasted.

every once in a while I could puddle a little but there was so much heat in there it would cool as i tried to touch my rod to the puddle.... I couldnt get the rod to go into a liquid puddle......yu know that grey haze that glazes over your heated zone, that tells you it is about to cave in!! ha ha

i saw that and got worried....truth is the pits i was trying to weld were not over a bore actually..they were over the last opening where the shift rod goes down through.

anyway. I wont try welding it any more..ill probably make more work for myself.

I wll try to find some marinetex..it should stick to freshly sand blasted surfaces.

I think my bigger issue might be the pitting on the drive shaft bearing dia...trying to figure how i want to deal with that with out buying a $500 plus drive shaft or buying a used one for $250 and getting the same problem i have now!!

bob

Post some nice close up photos of that and let's see if we can come up with something.

Mark_VTfisherman · Mar 28, 2009

Re: is there a secret to welding cast aluminum?

jay_merrill said:
...but you also have a material that isn't solid, so burn through occurs easily...

The density and the alloy together make this hard to do. I am not set up for aluminum, so I don't remember from the welding course, but if memory serves me preheating it is helpful.

Filler sounds like it would have a much better success rate though.

fakeplay · Mar 28, 2009

Re: is there a secret to welding cast aluminum?

Did you ball the end of your electrode ? You should be able to fill in aluminum flawlessly.

kenmyfam · Mar 28, 2009

Re: is there a secret to welding cast aluminum?

fakeplay said:
Did you ball the end of your electrode ? You should be able to fill in aluminum flawlessly.

See post #13 for your answer to that question.

bob johnson · Mar 28, 2009

Re: is there a secret to welding cast aluminum?

I filled in the whole area with Marine-Tex..and it is some tough stuff!!! I am almost finished sanding.....I only wanted to weld it to make it smooth, so it looked betetr after I painted it.

Ill post up some photos as I put her back together.

bob

is there a secret to welding cast aluminum?

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