Tig Welding Aluminum Boat Prop

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Today’s weekly video is tig welding aluminum edge welds with a few extra things thrown in to make things interesting.

A few weeks ago, the video was on mig welding edge welds and for a practical example, I used a tiller tine.

Building up the edge of anything is easier if you have a piece of copper to use for a backing material.

Copper has such a high thermal conductivity that it will not only draw heat away from the weld, but it won’t melt to the weld either. (unless you go nuts with heat like spray transfer mig or high amperage flux core)

A copper backing plate also helps to trap argon shielding gas. Without it, the argon has can get split over the edge and shielding can suffer.

So this week, a common weld repair on an aluminum boat prop shows how using a copper backing plate helps things go better once again.

Now for a disclaimer: Anything beyond a minor weld repair on a boat prop and you should be aware of balancing issues, pitch and rake, and also inspecting the hub. I am not recommending this repair… only using it as an example of an aluminum edge build up using tig.

4145 aluminum tig rod is a good choice for aluminum castings. It contains more silicon than 4043 and therefore melts quicker, flows better, and is less likely to have porosity in the weld. Your local welding supply will probably look at you like you have 2 heads if you request it so you might want to order it online. I have seen it on ebay as well as amazon and also arc-zone.com but sometimes there are minimum quantities required.

I also like 4047 for aluminum castings. Not quite as strong, but it flows great.

Also, for a wealth of info on boat prop repair, a good resource is rundquist.com.

For someone living on the water, there are opportunities for starting a business but be aware there is a substantial investment in pitch blocks and other tooling.

For this weld repair I was using an Everlast powertig 210ext. It’s a small tig inverter with a lot of settings… but I only used basic aluminum settings.

• Amperage was set to 135, but I probably never got over 80 amps using the foot pedal to control amperage.
• I used a 1/16″ (1.6mm) 2% lanth electrode tapered just about like you would for steel.
• 1/16″ (1.6mm) 4043 filler rod ( 4145 sometimes works better but I did not have any on hand).
• AC balance was set to -15 which is comparable to 65% en on a Miller or Lincoln inverter.
• AC frequency was set to 120 to help focus the arc ( 100-120 hz is a good all around setting for most jobs)
• #7 gas lens cup with about 15cfh argon flow

Before welding the boat prop, I decided to try out those settings on the edge of a thin piece of aluminum sheet.

After lighting up the first time, it seemed a bit hot on start so I went into the background menu and set the start current to give a soft start for edge welding on thin metal. After that, the starts did not even nip the edge. That was nice since a lot of tig welders in this price range of under $2000 USD are kinda hot on start. Remember the Miller Econotig? Decent machine but it started the arc way too hot for welding thin metal.

The video shows how using the copper backing makes for a cleaner weld puddle due to better argon shielding. And also the edge of the copper can be used for a guide to let you know when you have enough weld.

Since this prop was aluminum and since aluminum is easy to grind, a bit extra weld just ensures there is enough to sand off and still have the original contour without any dips, nicks, etc.

Well, that’s about it for this weekly video. Hope to see you here next week.

( As always, feel free to visit us at our sister site, WeldingTipsAndTricks.com. )

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