Cleaning Your Own Boat’s Bottom

By Tom Neale, 7/8/2013


Tom Neale's logs have a new name and home on BoatUS Magazine. We know Tom has a loyal and devoted readership, so we wanted to share his tips and insights with an even bigger audience! For the latest articles, click here for Onboard With Tom Neale.

What do you think about while you're under water under your boat working on the bottom? I just spent two hours doing just that, sucking air from a compressor up on deck. My boat is in waters that are muddy. There's been a lot of rain so the waters are very muddy. And it's dark — very dark down there, especially under the boat. What do you think about?

Is that an eel or a snake? It could be a snake. But do I really want to know?

Ready to do the bottom
Ready to do the bottom.

If it's a snake is it a water moccasin or a water snake? What is a water snake anyway? Smug people standing safely on the docks always say, "Oh that's just a water snake" when we see them winding along the surface. Wouldn't a water moccasin be a water snake? It's certainly not a water chicken. And then they say, "Well look for the triangular head." You kidding me? I couldn't tell the shape of that head if it was two inches in front of my face. (Please don't.) It's dark under there. I wonder if water moccasins bite under water? Brave friends standing safely on the dock say, "Oh, no, they don't bite underwater." I've heard a lot of stories to the contrary. So if they bite underwater do I really want to find out?

And I silently keep on working, scraping barnacles off the propeller. Silent except for the breathing bubbles. Do snakes ever make bubbles?

I know I've got to clean the V strut after I finish the propeller. You do this mostly by feel with your hands covered with heavy rubber gloves. And I can feel lots of barnacles on the V strut. OUCH. I forgot. Why is it that crabs always like to hang out in my V strut? And why can't they be little crabs? When I pull up crabs with chicken necks from the dock they're always little. Why don't these huge crabs ever leave my V strut and go for the chicken? And so I shoo the crab away with my scraper. He comes back. I do it again. At least it isn't a snake. I hope.

I return to work. What is that biting me on the back? I can feel it even through my wet suit. So it isn't a minnow. They like to nibble at fingers and toes and sometimes they can even hurt, but this isn't a minnow. And it's biting my back. It's another big crab. Maybe next time I should bring down some chicken necks with me. They seem to scare the big crabs away.

Tom's Tips
Tom's Tips About Diving Your Bottom

1. If you go swimming around your boat, do a little bottom checking if your skills and health are good for it and if it's safe. Even a few barnacles, especially on running gear, can slow you down.

2. Don't do this at a dock or boat where AC electricity is on. Take full precautions in this regard. Read the article entitled "ESD Explained" in the July 2013 edition of Seaworthy. Type ESD into the search block in the upper right hand corner of the BoatUS site and read all the material there about this very serious danger.

3. A paint scraper is usually a good tool for cleaning your prop and strut.

4. If you wipe slime off your hull with a rough rag or brush, you may take off more paint than you wish and shorten the life of your paint job.

5. I usually scrape off slime with light swipes with a wide paint scraper. The slime peels off leaving the paint underneath relatively untouched.

6. If you have an ablative paint, it's even more important to use the above procedure unless you think the paint needs some help.

7. Normally ablative paint sheds its outer layer as the boat moves, leaving a fresh "outer" layer ready to work for you, but as it gets older, a light wiping with a rag or brush may help.

8. New paints, such as Interlux Ultra with Biogard have ingredients that resist slime as well as growth and barnacles.

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And I move forward under the rounded belly of my boat, toward the bow thrusters. The barnacles love to hang on to those propellers too. And I'm thinking about the dynamics of this job. You know, don't you? You've thought about it already. This job isn't out in the wide open dark spaces like cleaning the propeller astern. This job is up in a dark, dark hole. Into which I have to put my hands. I get to the hole on the port side of the boat and peer in. I can barely make out a little dim light on the other side — very barely. All I see is the vague shape of the propellers, distorted because of all the tightly clinging barnacles. Wait a minute. Did something move in there? I foolishly hold my breath. The bubbles stop. This isn't good. I couldn't hear anything if it was moving in there anyway. I start breathing again and peer into the hole, letting my eyes slowly adjust to the blackness. Something moved! It's coming my way. Another crab, so big it can barely get out the hole. It changes its mind and backs out on the other side. Crabs can back out well, and also move sideways. Which it did as soon as it got out, coming back into the hole to confront me with its huge pinchers waving in front of my mask. I realize my eyes have adjusted some and I'm seeing better now. I don't know if I'm happy about that. I take my long screwdriver and jab at the thing. Something crunches. Was it crab or barnacles? It was probably barnacles because I realize that the crab is tightly clamping down on my screwdriver. "Gimmee my tool back, dammit." I shake it and he shakes back. Then I can tell that the crab is gone. I put my hand in the hole, holding the scraper, and begin working there. Of course I can't see into the hole when my hand is in there. Is something going to come in from the opposite side? I keep scraping, knowing I'll soon move under the boat to work at that opposite side. That's a problem with bow thrusters. They have two sides, two propellers, and double the terror.

Then I move on to the next phase: replacing the zincs. You know the score. Why do they make zinc bolts so little? I wish they would just clamp on. Holding the two halves of the zinc and holding the zinc bolts and nuts and holding the allen wrench one feels a bit shorthanded. And you're doing it with gloves. But long ago I swore to never use any zinc but a Camp because they have a little plastic washer that holds in the bolt and the nut is held in place also. Perfect. If I just didn't have to wear gloves. But do I want to take them off? No. Will I find my allen wrench if I drop it? You got to be kidding. Will I find the zinc half if I drop it? I won't even look. I buy lots of extras just for that purpose.

Then I move on to the big plate zinc. It's called a "Diver's Delight" because the zinc is formed around two stainless steel strips with long slots in them. You don't have to worry it on over the bolts coming out of the hull. There's a lot of wiggle room which is good when you can't see and you're holding a nut in one hand as well as the zinc in both hands. The zinc weighs a ton. But it becomes much lighter as I get it under water. I swim along with it, heading to the stern. Suddenly I plow into the mud. It didn't become lighter. Actually it added enough weight to me that my slightly positive buoyancy became very negative and when I thought I was swimming along I was diving like a submarine being strafed until I hit the bottom. It's easy to lose your orientation when you can't see. Luckily I don't let go of the zinc when it tries to disappear into the mud. That's a very expensive zinc. I struggle upward with it, wondering if I'll hit my head on the propeller. I don't. I hit my head on the bottom of the boat.

After that job, I go looking for holes. The thru-hulls. Inside they're black. Outside it's almost black. Where are those holes? I know how many are supposed to be there and I have a general idea where they are, but I can't see them. I feel. When I find one I go to work with my carrot peeler or oyster knife, clearing them out. Deep under the hull. Wondering what would happen if the compressor were to stop. Wondering if I really ought to exhale this next breath. But I have to because my mask is leaking and I have to blow the water out.

Why don't I just hire a diver next time, I ask myself. I know the answer. I'm having too much fun.



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