How to Weld a Cast Iron Marine Engine

Muggy Weld customer Scott Yeges recently pulled this cast iron marine engine from a scrapyard and noticed the starter mount was broken at the corner. Unfortunately, this is a common occurrence typically caused by either mis-mounting the marine engine simply knocking it over, damaging the mounting brackets. We frequently receive calls asking how to repair damaged marine starter mount brackets, and now thanks to Scott, we can now share his story for our customers’ benefit.

In this video, we feature Scott’s marine welding process, and this is Scott’s accompanying narrative:

This used motor from a wrecking yard appeared clean and tight. I did not trust the scrapyard to weld the broken starter mount bracket, so I purchased 77 electrode from Muggy Weld and attempted to weld the cast iron myself.

I used a 40 year old Sears and Roebuck buzzbox without any problems. I preheated the engine a little prior to welding.

The first weld pass flowed well. I welded roughly an inch at a time. The Muggy Weld rod built up well, no issues at all.

I used a needle scaler to remove slag from the weld. Very little porosity. Finished nicely! Repaired it in my garage!

Thanks, Muggy Weld; your welding rod is incredible. It made for an easy repair for something I was dreading. And I have already told some guys about your product.

Thanks again,

Scott Yerges

And thank you, Scott, for sharing these marine engine weld photos with our customers. Scott further noted:

I found the marine engine, fixed the problem after I identified it. I then used the swing set I built to install the motor. Then sent my son and family back home with a great running boat.

Tip

Be sure to bevel the crack with a grinder or Demel tool prior to welding, to enable the 77 rod to anchor to the base metal.

Disclaimers:

Please visit https://www.aws.org/Standards-and-Publications/Free-Resources/#YourResources prior to using our welding products, and adhere to all AWS welding safety guidelines.

Further product safety information is available at https://muggyweld.com/safety-guidelines

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MSDS sheets available with purchase from MuggyWeld.com, upon request.

Updated 11/23/25