PS Advisor February 2018 Issue

Which Bottom Paint for a Watertender?

I have a West Marine Watertender 9.4 with a polyethylene hull (versus polypropylene for the Walker Bays) and am wondering if there is an anti-fouling paint that is suitable. Looking through the product info for both, the manufacturers both claim that the plastics are slippery enough to not need paint, however, the plastic wrap (unknown material) on the wooden pilings on my own docks in Florida have marine growth on them, so I suspect the same will happen with my Watertender (currently stored on the dock).There are conflicting reports/opinions on various forums as to if there is a paint that would actually stick to the hull, as well as potentially damage the plastic.

Don Keskula

Punta Gorda, Fl.

Com-Pac Sunday Cat

Most cruising sailors use their dinghy enough or pull it out of the water frequently enough that barnacles and slime aren’t a major problem. A ½-hour scrub every couple weeks in the tropics kept our editor’s hard dinghy clean. But if you are staying in one place for a long time, bottom paint can save you the hassle of having to beach the boat.

Here’s what Interlux paint’s tech staff suggested. According to them, this is basically the same protocol for a polyethylene hull like the Walker Bay.

“The system to apply the antifouling to the polyethylene hull of the West Marine Watertender would be the same system that is used on a polypropylene hull.

1. Clean the hull with Fiberglass Surface Prep YMA601 it is a water-based dewaxer and surface cleaner. It is applied by a 3/8” nap roller and then scrubbed with a brown or maroon 3M Scotchbrite Pad. 

2. Sand the surface with 80 grit sand paper; make sure you change paper as needed to ensure a consistent sanding pattern.

3. After the sanding residue has been removed,

4. Apply two coats of Fiberglass Bottomkote Aqua antifouling.

The reason that you want to use the Fiberglass Bottomkote Aqua is because it is a water-based antifouling paint and will be the most compatible for the hull material.”

It is also worth noting that Bottomkote Aqua is a hard bottom paint, so it won’t easily rub off on you when it is on your deck. Most other water-based paints are softer, ablative paints.

Previously, owners of Walker Bay PVC hulls were advised to use Interlux VC-17, preceded by a solvent wash and a no-sand primer. We presume this advice also still holds.

The experts from Pettit advised a slightly different approach. After scuffing with sandpaper and then wiping with a solvent, the blue “oxidizing” portion of a propane torch flame is quickly passed over the hull—as if spray painting. This is followed by 6999 Sandless Primer, or 6980 Rustlok Primer, then bottom paint. The priming and painting must occur within two hours of flame treating. Any oil-based antifouling can be used, according to Pettit.

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