lower units...skegs

[blackwire]

I'm new to aluminum welding and am doing a few skeg jobs.What do you use to sand paint off and bevel pieces to be welded?(without contaminating the aluminum).

[Hardrock40]

I'd say pretty much anything you want to use. You can run your disk across a wax candle to keep it from loading up to much.

Personally I wouldn't worry about contaminants on a skeg. Your most likely going to see black crap floating out of the base aluminum.

If the lower unit still has the prop shaft and gear housing seals in it that would be more of a concern. Use high heat to get the weld going quick and let it cool some when it gets hot. Maybe some wet towels will help cool the gear housing.

[blackwire]

Yeah I was wondering what to use..my aluminum oxide flappers embed the aluminum(I wax them too),I found 3M surface conditioning disks work.Just looking for some tricks here.How about cutting the skeg material and the lower unit..I use my plama on thr cast,but saw cut the blanks...any thoughts?

[Bistineau]

There are grinder discs made specifically for aluminum you could try instead of the flap discs. These do not load up like the standard type disc do. Check at your LWS for them, someplaces you may have to ask them about it as they don't always keep them out on the shelf.

[MMW]

A carbide bit in a die grinder can also work depending on the application.

[sturugged]

Hello, I have had good luck using flapper or sanding disks to remove the paint off the lower units. Once the paint is gone , regular grinding wheels or zip-cuts with bees wax to stop them clogging up for grinding or cutting the base aluminum. As for cutting the new patch pieces or material , I use a small wood cutting bandsaw for making up patch pieces or shape cutting, its alot cleaner cut than the plasma and there is no cleanup required, before welding it. You can even bevel your pieces nice if you want to get real fancy. For just breaking up the oxide layer and between passes i use a blue Walter stainless steel wirewheel on the grinder for buffing off the welds. This works good if you do get the black junk contamination . hope this helps

[blackwire]

Thanks for the tips...I found my plasma left a roughish edge there too,the band saw idea is great-that should help things go ceaner & maybe bevel at the same time.My buddy sandblasts the paint off-I'm not so sure about doing that tho, with the silica sand.Things usually go pretty well,but we are still dealing with cast aluminum of varying qualities.

So what do guys like for skeg material?I use either 5053,6061,but am wondering about the pre-cast ones.Sure seem expensive but maybe savings can be had from less shaping time.Are these pre-cast skegs free of junk inside them?

[Portable Welder]

By the way good luck on your welding, You might want to practice on some old aluminum first.

[Hardrock40]

The replacements are probably cleaner metal than the original. Kind of like aluminum props, some are clean and some are trash. Don't worry too much about a skeg. Get some aluminum filler paste for any pinholes that may not sand out.

If its not to bad, straighten it with a hammer ( a heavy soft hammer) over something to provide backing support and just weld it out, then finish it down to the original look.

If its over half gone, that may not be an option. You need these things removed from the engine where you can work on it. If its broken off up close to the housing, seals will most likely need to be replaced afterwards, tell the owner so they know ahead of time.

I have welded them for a prop shop, it is not that bad. Don't overthink it and worry with it. Don't know what your welding it with but you'll need some power if its up in the thicker area.

4043 works ok for filler.

[blackwire]

Yeah I've played around on corroded cast aluminum,sure shows up some interesting things!lol!I was using a Precision Tig 225,but not enough power,welds good,harsh arc however.So I just ordered a Synchrowave 250dx,I tried an older one at work & liked it.Just as mentioned,the need to puddle fast on thick sections to lower overall heat input will be great.So far none (skegs) have fallen off leaving the dock..lol!Some that have been re-hit bent over & didn't break,happy about that.The biggest gearcase so far was a 150hp,but I didn't have to replace much.Ok I appreciate the advice & need one more opinion(for now).Where do you ground the welder on gearcase?Is there anything to the idea that current thru the bearings is bad?I was given two differing opinions around here