Skeg Welding

[andrewss]

Bought an older Mirrorcraft aluminum fishing boat a couple years ago with '89 Merc 60 on it, been using the boat and fixing it up as I go. Fires up and runs great even sitting over night below freezing; 105psi compression across the cylinders. Good hole shot and 33mph top. Electrical and lines all look good.
But there is only about 1/3 the skeg on it, so i bought an repair plate and going to get it welded on.
The person doing the welding has lots of aluminum experience. But because of heat they are pretty adamant about stripping everything out of the lower unit. Every YoutTube video I've watched claims you don't have to remove anything, and suggests leaving the gear oil in as a heat sink, and some use wet cooling rags to also help. I also called two local marinas, one was good'ol boys and said they don't pull anything except the prop, the other shop said "you'll have to bring it in so we can take a look" not the answer to my question but I get it, no free lunch.
And looking on Kijiji (Craigslist) at the guys advertising skeg repair, all their pictures show the welding setup with prop and everything still on.

What is the forum consensus?

 

[FunInDuhSun]

I had it done many years ago by a local fab shop, didn’t even take the prop off.

 

[flashback]

I would leave it as is.

 

[Scott Danforth]

my last skeg repair was like this:

drop boat at marina.

go to lunch at the restaurant next door

guy pulls vent plug on side of boat and screws in a fitting and hose and clips it to the transom. this prevents the seals from blowing out as the oil expands from heat

guy takes repair skeg lays next to my skeg, marks the stuff to trim off and cuts with a 3" cookie wheel

guy preps skeg nub and repair piece

uses 1/2 pound of cold putty on gear case to control heat

welds skeg by skip stitching

grinds weld

and paints while still warm.

looks factory fresh

I finish lunch, pay the guy and am in the water 35 minutes after he started

 

[ahicks]

Guys with some experience that do this routinely are pretty good at it and don't take all day doing the welding. Kinda routine here on the Gulf side of Florida. I could see guys that have never done one being a little shy of the project.

Another way of looking at this, maybe a mechanic's take? An '89 is way past due to be resealed anyway (over 30 years old?). Kill 2 birds and pull it down for new seals and get it welded while you're at it.

 

[dingbat]

Unit could be left on the boat and welded under water if you wanted to. All depends on the skills of the welder. Lots of “unskilled” practitioners (lack formal welding training and or certifications) out there.

Personally, I prefer the customer remove the unit so the work can be done on the bench. Makes the job quicker, easier and all but eliminates any concerns with grounding issues.

Making it easier on my back makes me go easier on your wallet….

Unless your welding foils, heat isn’t an issue welding aluminum. In fact, aluminum dissipates heat so well it’s hard keeping enough heat in the weld zone. Larger assemblies often benefit from preheating, if nothing else you preheat to burn the contamination (paint and oil) out of the weld zone before welding.

The bigger issue would be burning up the electrical system or arc spotting a bearing in the lower unit. Seen some bad things happen when you connect a 150-200 amp DC potential to a vehicle’s electrical system.

Disconnecting the cables from the batteries is a critical step in protecting the vehicles electrical system

 

[andrewss]

Thanks for the input!
I have the lower unit pulled, water pump kit on order.
I replaced the lower unit oil seals just in August.

I think what I'll do is remove the vent plug and use putty as mentioned above or cool rags on the prop shaft housing, then just keep an eye on temps as we go.

 

[racerone]

Whenever welding is done on a component there is a risk of distortion.------A welding shop that does these all the time would have a procedure in place.----Or they have likely made mistakes over the years and do not make them anymore.