By Christian Herold, Certified Professional Yacht Broker
When it comes to boat projects, some decisions are purely cosmetic—like the color of your boot stripe. Others directly affect safety. Thru-hull fittings fall squarely into the second category. These small but critical components penetrate the hull, often below the waterline, and if one fails, the consequences can be serious. Choosing the right material matters.
I think it is appropriate to disclose a little of my background and qualifications to write this article. I am a retired U.S. Coast Guard officer with extensive operational and inspection experience, including service as a Marine Inspector responsible for evaluating small passenger vessels, foreign-flag cargo and tank ships, and U.S. towing vessels. I am ABYC Standards Certified and a graduate of the Chapman School of Seamanship’s Yacht and Small Craft Surveying program, though I do not actively conduct vessel surveys.
I was recently involved in a survey where a friendly debate arose over whether anything other than bronze belongs below the waterline. That conversation prompted a closer look at the issue—and at what the standards actually say. According to ABYC Standard H-27, the focus isn’t on material at all. Instead, the standard requires that any thru-hull fitting below the waterline must withstand 500 pounds of static force for 30 seconds without failure and must include a proper means of shutoff, typically a seacock.
With that in mind, let’s take a practical look at the two most common options: bronze and Marelon…
