How do you keep bugs out of your boat when it’s on the hard? Whether it’s in storage or you’re living aboard in the work yard, bug intrusion can be a major problem.
Bugs love to enter boats through the thru-hulls. 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.
How to Keep Bugs Out of Your Boat’s Thru-Hulls
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? They told us exactly how they used the stainless scrubbers to easily keep bugs out of the thru-hulls.
It works even better than screen and is much easier to do. Win-win!
- Cut each stainless scrubber into a couple of chunks (depending on how large the scrubber is and how large the thru-hull) with regular scissors.
- Stuff one chunk of the scrubber into each thru-hull, keeping the outer edge flush with the hull of the boat so that bugs can’t build nests in the thru-hulls or get into the boat. You want the thru-hull to be firmly blocked off. Air and water will still seep through.
- Do all open thru-hulls and those that are closed so there won’t be any nests in the inch or two between the hull and the valve.
- Remove them all (and open any closed thru-hulls) just before putting the boat back in the water.
Where to Buy Supplies
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! Don’t try to use green scrubbies as they are not flexible enough and will leave gaps that bugs can crawl through.
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 expensive anywhere. It took two 3-packs to do our whole boat, and we had some left over.
This article was originally written in January 2016 and was most recently updated and made more detailed in February 2020.
Debbie Williamson says
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 says
Dave Tew says
I put a small spongy nerf-type ball in the engine exhaust also.
I do this very thing for my shower sump, works great
Shireen Beeson Reynolds says
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 says
We use bronze wool. Cheap at Ace Hsrdware.
Rebecca Tommaseo Ponzetta says
Luigi, for Night Flower on the dry
Linda Schrank says
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
What ever happened to good old fashion corks?
Carolyn Shearlock says
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 says
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 says
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 says
Not only bugs, snakes too!!
The Boat Galley says
I don’t even want to think about a snakes getting in our boat . . .
Frank Kleinburg says
Great idea.. flk k
That’s a fantastic idea
I like it
Great idea. We will use this, this summer
Jennifer Guerrero says
What about using steel wool?
Carolyn Shearlock says
It will rust and leave stains. Use stainless (best) or plastic.
Rick Scaggs says
Have a bamboo skreewer to remove the spider nest in the fuel vent. If you don’t vacuum drag will cause your engine to fail at the worse possible time.
Carolyn Shearlock says
Amy Alton says
Great advice! We just did this to our boat and I hope it works out!