How to Repair a Broken Cast Iron Marine Engine Starter Mount

A broken starter mount can complicate plans to put a used marine engine back into service.  Muggy Weld customer Scott Yerges found a cast iron marine engine at a wrecking yard that appeared clean and tight, but a corner of the starter mount bracket was broken.

Scott decided to make the repair himself using the Muggy Weld 77 electrode.  He completed the welding in his garage with a 40-year-old Sears and Roebuck buzzbox.  His repair combined a little preheating, weld passes of roughly one inch, and slag removal with a needle scaler.  After repairing the mount, he installed the motor and sent his son and family home with a running boat.

Inspecting the Broken Starter Mount

The starter mount was the damaged area Scott identified on the used engine.  Rather than trusting the scrapyard to weld the broken bracket, he purchased 77 electrode and took on the cast iron repair himself.

Muggy Weld often receives questions from customers facing similar damage to marine starter mount brackets.  Improper mounting or accidentally knocking an engine over can damage these areas, although Scott’s account does not identify what caused the break in his engine.

For anyone looking to weld a cast iron marine engine, Scott’s experience provides a specific example: repairing a broken mounting corner with stick-welding equipment in a home garage.

Preparing the Cast Iron for Welding

Before welding a cracked or broken cast iron area, bevel the joint with a grinder or Dremel tool.  Beveling opens the repair area so the 77 electrode can anchor to the base metal and fill the prepared joint.  Scott also reported that he preheated the engine a little before welding.

Building the Repair with 77 Electrode

Scott used his Sears and Roebuck buzzbox to apply Muggy Weld 77 to the broken starter mount.  He reported that the first pass flowed well and that the rod built up without problems.

He welded roughly one inch at a time as he built the repair.  That detail is especially important because the job involved filling a damaged mounting area, rather than simply joining two flat pieces of metal.

Scott described the process in his own words:

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

Installing the Repaired Marine Engine

Once the starter mount was repaired, Scott used a swing set he had built to install the motor.  He then returned the boat to his son and family.  His follow-up described the outcome:

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.

Scott’s repair addressed the broken starter mount on an otherwise promising used engine.  Muggy Weld 77 allowed him to build up the damaged cast iron area, finish the weld, and proceed with installing the motor.

Thank you, Scott, for sharing these marine engine weld photos with our customers.

Disclaimers:

Before using Muggy Weld products, please review and follow the welding safety guidelines provided by the American Welding Society (AWS):  https://www.aws.org/Standards-and-Publications/Free-Resources/#YourResources.

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

Muggy Weld LLC shall not be liable for any loss, injury, claim, liability, or damage of any kind resulting from or related to (a) the use of this website or its contents, (b) the use or misuse of any welding products or services obtained through this website, (c) errors in or omissions in the information provided, (d) the unavailability or interruption of this website or its features, (e) reliance on any instructions, techniques, or demonstrations presented on this website.

Safety Data Sheets (SDS) are available upon request with purchase from MuggyWeld.com.

Updated 10/13/26

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