spool gun or tig?

[aluminumdreamer]

Here is the thing, my boat was an inboard jet, and now has an outboard bracket with an outboard on it. So I have this big engine box taking up all this valuable deck space in the back of my boat. I have a pretty good plan to remove it, and make it flat with a flush mounted hatch for access. Here is where my problem lies, I don't know how to weld aluminum yet. I do however have a friend that has access to a spool gun, and he knows how to use it. I know that tig welding it will look much nicer, but that really isn't a concern considering my boat is an older work boat with alot of shitty looking welds to begin with.

Can anyone come up with a good reason why I should not proceed with the sawzall and the spool gun? Keep in mind that I can smooth the welds, and I plan to nonskid coat the floor. Also my boat is not a Pacific and does not have the fit and finish of a higher end alloy boat.

[Chaps]

There is no good reason in your case to use tig. A mig machine with a spool gun and someone that knows how to use it is perfectly suited for the job.

Keep in mind that welding of old, weathered aluminum is challenging due to the oxide layer and other crud that slowly imbeds itself into plate alloy over the years so after you do your sawzall surgery you need to thoroughly grind (sand, wire brush, etc) all the points receiving new weld to bright, clean metal. Make sure your abrasives or brushes are new and clean and in the case of brushes stainless steel. After abrasive prep then scrub the areas with lacquer thinner or some other hot solvent that doesn't leave a residue of any kind. Weld within a couple of hours after this prep work.

The bigger boat in my sig used to be an inboard, it has the same process done to it that you are about to do.

[aluminumdreamer]

I have seen the pictures of your boat and the work it has undergone. It is my inspiration. Your boat is pretty incredible, and I can only hope mine comes out half as well as yours did.

I have some 3m 36 grit sanding discs for my die grinder do you think those would be a good means of prepping the surface? They may be too rough I could always get some 60 or 80 grit. I have some time before I actually do this job, I've only owned the boat for a month, and the wife is already asking if there is an end in sight. So I may be running it how it is for this season, and then do some major surgery over the winter. Also may not be a bad idea to wait, I going to try to take an adult education welding class. A co worker of mine has a tig I could use, so it may be best to hold off for a bit.

Thanks for your input,
Nate

[welder]

Dollar wise, use the spool gun.
As said above , CLEAN very good and this will equal a much better weld and easier clean up.

When sanding Alloy remember .........It can go away real fast. just keep the sander on the weld , NOT the parent metal and I'm sure you will do some type of groove weld with backup bar , right.

[keith]

If you're just trying to clean the metal for welding I would use a 120 grit flapper disc. They don't clog up as fast as a regular disc and remove material surprisingly fast. Save the 60 or 80 grit for smothing welds.