Putting screen in all the thru-hulls works to keep the critters out, but it's a time-consuming nasty chore. Turns out there's a much easier way to keep them out!

Don’t Let Bugs in the Thru-Hulls

So your boat is out of the water. Whether it’s in storage or you’re living aboard in the work yard, bug intrusion can be a major problem.

Sure, some of your thru-hulls can be closed. But probably not all.

Vents for the fuel and water tanks probably can’t be closed, period. And you may not want to close up sink drains if you’re living aboard and/or have a dehumidifier running. You may want to leave the thru-hulls for the bilge pumps open, too, so that if rain gets in the bilge pumps can get it out.

The “open to the inside” thru-hulls can let ants, roaches, bees and more into the boat. Not good.

But even the thru-hulls that don’t directly open to the boat interior can pose a problem. Where we were hauled out on the northern edge of the Everglades, paper wasps and mud daubers were a huge problem and would totally close off tank vents. We saw more than one boat discover that they had to dig hardened chunks of mud or nests. One boat discovered that their bilge pump wouldn’t work when they re-launched . . . when they took it apart to rebuild it, they found a mud dauber nest.

Our first year there in storage we were advised to stuff screen in all the open thru-hulls and vents. It worked well – air or water could still flow but the bugs were blocked – but it took Dave forever to do and he really scraped his hands up between cutting the screen up and stuffing it in.

The second year, Terry and Jenn Pierson were getting their boat ready for storage at the same time we were. I was heading into town one day and asked if they needed anything. Sure – stainless pot scrubbers to plug the thru-hulls. HUH?

Terry explained that he just cut them into a couple of chunks (depending on how large the scrubber is and how large the thru-hull) and stuffed them in. They cut with regular scissors and don’t scrape your hands up.

So we bought not only some for them, but for ourselves as well.

It took Dave about a half hour to do the whole boat. Plus he did all the thru-hulls that he’d closed, just so there wouldn’t be any nests in the inch or two between the hull and the valve. We’d discovered a few there the previous year. So, so much easier!

You can find the stainless scrubbies in most grocery stores – just be sure to get stainless ones or they’ll rust out after the first rain! They’re a little cheaper on Amazon than at the grocery where I bought them (everything is more expensive in south Florida) but they’re not frightfully high anywhere. It took two 3-packs to do our whole boat, and we had some left over.

Putting screen in all the thru-hulls works to keep critters out, but it's a time-consuming nasty chore. Learn a much easier way to do it!

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  • Debbie Williamson
    Posted at 29 January 2016 Reply

    I scrunch up crinoline netting, wrap a long zip tie around it as a handle and stuff it into the thru hulls. The zip tie tail sticking out of the thru hull reminds me to pull it out before we splash

  • Frances Liz Fernandez
    Posted at 29 January 2016 Reply

    Good tip

  • Dave Tew
    Posted at 29 January 2016 Reply

    I put a small spongy nerf-type ball in the engine exhaust also.

  • Wayne
    Posted at 29 January 2016 Reply

    I do this very thing for my shower sump, works great

  • Shireen Beeson Reynolds
    Posted at 29 January 2016 Reply

    These work great in the home as well to plug any areas you don’t want insects or rodents to get through. Rodents can’t chew them….

  • Bill Dixon
    Posted at 29 January 2016 Reply

    We use bronze wool. Cheap at Ace Hsrdware.

  • Rebecca Tommaseo Ponzetta
    Posted at 30 January 2016 Reply

    Luigi, for Night Flower on the dry

  • Linda Schrank
    Posted at 04 February 2016 Reply

    Loved the stainless steel idea. Had some laying around and have stuffed pieces in places where I have a wasp problem. Will also try them where mice tend to get in. I’m a farm gal, but your boat tips work well for off grid high humidity areas

  • tom
    Posted at 19 July 2016 Reply

    What ever happened to good old fashion corks?

    • Carolyn Shearlock
      Posted at 19 July 2016 Reply

      We can’t totally block off the thru-hulls when we’re on the hard — if there is a leak in the rain and the bilge pump runs, we want the water to exit the boat. People who use dehumidifiers have the same thing — they run the drain on the dehumidifier to the sink, but if the sink is corked off, the water would just back up into the boat. Hence the need for something like screen that will let water through, but not bugs.

  • Keith & Nicki - s/v Sionna
    Posted at 20 July 2016 Reply

    Another great idea – thank you! Sionna is about ready to go, and we’re frantically tying up loose ends and planning a mid- August departure south. Who knew going cruising would be this much work?!
    Well ok, you did… 🙂

  • Sherry Matas
    Posted at 03 April 2017 Reply

    Squishy golf ball cat toys work really well too. Just squeeze to pop it in and it expands to the size of the hole.

  • Terri Zorn
    Posted at 16 May 2017 Reply

    Not only bugs, snakes too!!

    • The Boat Galley
      Posted at 16 May 2017 Reply

      I don’t even want to think about a snakes getting in our boat . . .

  • Frank Kleinburg
    Posted at 16 May 2017 Reply

    Great idea.. flk k

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