[VictorOscar]

Hey, was hoping for some advice on welding on a painted aluminium boat.

The big question is can I weld on the boat with the motor still attached?

One of the areas I wanted to weld was on the transom maybe 6 inches from the motor and I was concerned but how close the motor was going to be.

The boat is also painted, how much paint needs to be removed around the areas I want to weld?

As a precaution I was going to remove the fuel tank, battery and disconnect all other electronic devices (ignition, sounder, radio etc.). Are all of these necessary and is there anything else I should be doing before starting as well?

I want to weld a few things on the boat and plug some holes but wanted to ask the experts before starting

Thanks,

[Sandow]

Well, a lot of this is going to be a swag but I'd think the motor should be fine but obviously you need to take precautions about fuel and fumes. I've welded on plenty of cars with everything still connected and never had an issue.

The welding is going to fry paint in a pretty decent radius. I'd clean 6 inches around the weld areas for good measure. Marine paints have some weird stuff in them that is probably not great to breathe.

One thing I'd point out though is that it may not be weldable at all. If it is 7000 series you are SOL. Look around, if there are no welds anywhere it may well be the case. 7000 series will crack pretty much instantly.

-Sandow

[VictorOscar]

Thanks Sandow,

The whole boat is welding together so I am certain it would be 5xxx series alloy.

Regarding the paint, I might take off the bait board (bolted on) and try a few welds on there before I start on the boat.

[AndersK]

A good rule is to place the return ("ground") clamp as close to the welding area as possible when welding anything with electronics or AC alternators connected.

[motox]

7005-7003 are weldable
7075 is not

[big gear head]

I've welded on several boats with paint. I clean about an inch on both sides of the weld. Cleaning out the crack is the hardest part. I've also welded them with everything still hooked up and didn't have any problems. I've welded directly on the engine without any problems. Keep the ground close to the weld and don't get electronics between the weld and the ground.

[VictorOscar]

Thanks for the advice everybody.

I'll hopefully get a chance to give it a go over the next few weeks - will let you know how I go!

[Braehill]

If at all possible, get to the back side and clean the paint off as well. A full penetration weld will pull the paint fumes through the cracks and into the cover gas envelope. That will cause you grief, as well as leave you wondering what went wrong. Cleaning out the cracks will be a challenge, all manner of nasty stuff gets in there if it's been under the water.

A small saw blade on a Dremel can make a very thin slice through the cracks to clean them out. Be careful, these are made to cut wood, so they grab. Use a slow speed so you can keep it from getting unwieldy. They'll go through a knuckle like they were made for it. Don't rush it or they will clog up quickly.

Good luck.

Len

[big gear head]

Yes, clean the back side. Very important.

[VictorOscar]

What do you reckon is the best way to remove paint?

I wanted to stay away from chemicals so was thinking sandpaper?

[Poland308]

I like scotch brite pads. You can get diferent kinds. I've got some that are almost like a wire wheel with a shank built in so I can chuck it up in a drill and run it real slow. You can get wire wheels that are SS but they can be hard on thin aluminum.

[ajlskater1]

Scotch Brite pads for a decent job of removing paint

[VictorOscar]

I like the looks of the scotch-brite pads.

Are the 7440's the best ones?

They're the tan coloured ones.

[AKmud]

A broken in flap disk works well. I don't like using new ones on boats since the aluminum is usually pretty thin and new flap disks can take a lot of material off quickly.

[aeroplain]

Boats are all I ever "get" to weld on. I use these with great success. http://www.nationaltoolwarehouse.com/3- ... aQod55IN0A

[Poland308]

I use the maroon ones cause that's what I bought a box of last. And I have some to go on my die grinder like the ones in the other post.

[kiwi2wheels]

These are great for paint removal.

http://solutions.3m.com/wps/portal/3M/e ... 681&rt=rud

http://3mcollision.com/scotch-brite-cle ... oarse.html

http://solutions.3m.com/wps/portal/3M/e ... 405&rt=rud

They used to be available, with an integral shank for use in a drill chuck, from better hardware stores and industrial suppliers.