Seal the Deck

Posted: May 1, 2014

Deck plate O-rings are simple and inexpensive to replace, so do it already.

By: Story and photo by Deane Hislop

With all the concern about water-contaminated fuel, there’s a ton of advice to be found regarding additives, filters and at what level to keep your fuel tank during storage. The empty-tank/full-tank debate rages on, and most of this advice is great, but nobody talks about the simplest preventive maintenance chore you can perform to keep water out of your fuel: Change the O-ring seal on the fuel-pipe deck plate. The rubber O-ring seals will become brittle and crack over time and begin to leak.


If you remove your fuel cap from the pipe and look above the threads, you’ll see the O-ring. It is simply a round rubber-type washer that seals the fitting, preventing rain, spray and wash-down water from seeping along the threads and getting into your tank. After a few years, five at the most, the O-ring should be changed. Just pop the old one off, lightly oil up the new one with multipurpose oil and fit it in place.

When it was time to change the fuel O-rings, I also replaced the freshwater fill pipe and the black-water tank’s deck plate rings. On my boat, they all use the same ring, so it’s as easy to replace four as it is to change two.

Where does one get replacement O-rings? Most major deck hardware manufacturers sell them as replacement parts. You can also find them at your local marine supply store — West Marine, for instance.

If you’re in a jam and need one quickly, you can take your old one to a hardware or plumbing supply store and match it up for diameter with what the store has in stock.

While you’re at it, change the O-rings on your deck plates. Deck plate O-rings — the round fittings that either screw or snap in place to provide access throughout the boat — get flat or damaged as well. No sense having “dry” fuel and a wet bilge, is there? If yours are pry-up models rather than screw type, there’s always some damage at the pry-up point. Again, check the manufacturer’s catalog for replacements. The maker’s name is likely stamped on the underside of the cap.

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