Welding on a crankshaft

Winston · Mon Feb 22, 2021 1:28 am

I want to weld up a gouged out key seat on an outboard motor crankshaft.
I am going to make a key out of copper to insert into the key seat, then fill in the gouged out area.
What I want to know is what type of filler material is recommended for this procedure. I will be TIG Welding.
Thanks for any responses in advance

Louie1961 · Mon Feb 22, 2021 2:55 pm

You can probably get by with ER70-S2, since a lot of cranks are cast steel. But I don't think you are going to get by without any post weld heat treat or machining. It seems like most of the shops that repair these use submerged arc welding, then do a post heat treat and machining.

cj737 · Mon Feb 22, 2021 3:51 pm

A copper key is a strange choice in my opinion. You can do build-up/repair with bronze or Eutaloy, but I don't think you'll need to post- heat treat for a small build-up repair. You're not getting enough of the crank hot enough to do any damage that I can envision.

Coldman · Mon Feb 22, 2021 4:01 pm

What's the material?
Can you post up a pic?

Louie1961 · Mon Feb 22, 2021 7:10 pm

cj737 wrote:You can do build-up/repair with bronze or Eutaloy, but I don't think you'll need to post- heat treat for a small build-up repair. You're not getting enough of the crank hot enough to do any damage that I can envision.

Crankshafts generally require about +/-0.003 inches of tolerance. Different alloys which expand at different rates are not going to be suitable. Likewise, you are not going to get those kind of tolerances by trying to reshape the crank by hand. Without post weld heat treat, he will be back doing the same repair after a few months of running that engine. It will definitely need to be hardened, if only because the weld material will not be as hard as the surrounding base metal.

cj737 · Mon Feb 22, 2021 8:18 pm

Louie1961 wrote: Crankshafts generally require about +/-0.003 inches of tolerance. Different alloys which expand at different rates are not going to be suitable. Likewise, you are not going to get those kind of tolerances by trying to reshape the crank by hand. Without post weld heat treat, he will be back doing the same repair after a few months of running that engine. It will definitely need to be hardened, if only because the weld material will not be as hard as the surrounding base metal.

No one suggested reshaping by hand. I merely stated heat treating is likely not required. And I will stand by that statement. Some marine engine cranks use completely different alloys that don't rely on heat-treating due to their immersion in saltwater environments and/or presence of galvanic corrosion. Hence, the suggestion for bronze

But since the OP has yet to post a picture or specifics of the damage and area to be repaired, general ideas are the best anyone can do.

Jakedaawg · Tue Feb 23, 2021 7:34 am

What motor are you working on? This is what I do. I have parts motors going back to 1935.

Winston · Fri Feb 26, 2021 5:03 pm

Coldman wrote:What's the material?
Can you post up a pic?

This is a 1999 Suzuki 60hp 4 stroke motor. The key seat is near the top of the crankshaft, outside the motor, where a gear for the timing belt attaches.
I am using a temporary copper key in hopes of it preventing any weld metal from flowing into the key seat.
The crankshaft is still in the motor, on the boat. The crankshaft is in the vertical position.

Coldman · Fri Feb 26, 2021 9:14 pm

A copper key to help shape the molten weld pool is a good idea.
Now that we know what the motor is, maybe someone will know what the crankshaft material is.

Jakedaawg · Sat Feb 27, 2021 5:57 pm

You absolutely will not be able to keep the top seal from being damaged. I would wrap that area in wet rags...

These cranks are a dime a dozen. Simple to tear down and replace with new bearings. I have done a couple. Those motors had a corrosion issue in a water passage. Any marine salvage yard will have several available.