PS Advisor January 2017 Issue

Bottom Paints for Freshwater Sailors

Bottom Paint Test
Only a few paints that we tested on Lake Superior had significant slime growth.

I am a relative novice to sailing, and my new-ish boyfriend is thinking about bringing his boat to Lake Superior, Mich. He’s one of those sailors who needs the best of everything, and he hopes to race, with me as crew. He asked me to inquire with the local racers what bottom paint they used, but there seemed to be no real agreement. Some use no paint at all. Does he even need any bottom paint?

M.M. Robinson

Upper Peninsula, Michigan

First, we need to address the real question you should be asking: Do you really want to race with this guy? Although we know many couples who make terrific sailing teams, we’d not recommend a trial-by-water to any “new-ish” couple—unless, of course, the aim is to lay bare any latent power struggles that exist. Nothing reveals character faster than a “friendly” race around the buoys. You are duly warned.

As to the bottom paint dilemma, that one is easier to answer. We’ve tested paints in Lake Erie (see “Freshwater Antifouling Paints,” PS March 2007 online) and have a number of readers with boats on Lake Michigan who report their experiences to us. Closer to your location, the Marquette Yacht Club recently allowed us to use a section of dock for hanging test panels coated with eco-friendly and freshwater paints; those results will be in an upcoming issue.

We do recommend applying some kind of antifouling paint unless the boat will live on a trailer. An unprotected hull on the Great Lakes, or any freshwater lake, is vulnerable to both soft growth (algae and slime) and hard growth (shellfish). Fortunately for you, Lake Superior is still mostly free of fast-growing zebra and quagga mussels, two invasive, fast-growing fouling organisms that have colonized the Great Lakes.

In our opinion, you should narrow the list of paint contenders to include only those that have low- or no-copper content or are slow-release, “hard” coatings that will minimize the potential harm to the more fragile freshwater environment. Copper-loaded ablative paints are overkill in almost any freshwater lake.

Fortunately, fighting slime alone doesn’t require a lot of copper or super-potent additives. One of the best-selling bottom paints in the Midwest, Interlux VC17, has just 17-percent copper. A standout in our Lake Erie test, Pettit’s SR-21 has 21-percent copper. In fact, some Great Lakes boaters have reported that they do just fine with an annual coating of a “moustache,” a 4-foot-wide stripe painted below the waterline (where slime growth is thickest), plus coating the entire hull with a multi-season, hard paint every two to three years.

Sea Hawk also makes its own brand of freshwater paint, Sea Hawk Silver Bullet. And West Marine sells a freshwater paint (rebranded Pettit paint) called FW-21. These thin-film, low-copper paints dry fast and create a slick, hard surface. A small amount goes a long way. The only trouble is that if you do decide to change paints to a conventional antifouling paint—something you’ll want to do if you move to a saltwater location—you will have to remove all the paint. Despite this drawback, opting for a less potent concoction in fresh water is more than just economical, it makes environmental sense. Smaller lakes, in particular, are more fragile ecosystems than well-flushed saltwater basins.

We publish an update on our bottom paint testing program each March or April. In our past tests, paints that generally did well in salt water also did well in fresh water. For the most recent report, just search “bottom paint” on Our results in Lake Superior will be part of the upcoming report. Spoiler alert, only a few of the paints had any slime at all. We’ll see how they do after two seasons.

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