More of this Feature • Keel Cooler, and more • Two-Stroke Acceleration Problems, and more • PMY Tries... FSR Big Job
Related Resources • Maintenance Q&A Index

How does a keel cooler work, and is there any special maintenance involved? M.L., via e-mail
A keel cooler is much like the radiator in your car. It extracts heat from engine coolant via a network of piping and transfers it to the surrounding environment. The difference is that in a car that environment is air, while on a boat it’s sea water, and instead of a radiator, a boat has a series of tubes attached to the outside of the hull. (On commercial vessels the tubes are attached to the keel, where they won’t snag nets or pots, but on pleasure vessels they can be most anywhere.) Keel coolers are usually found on displacement-style vessels, where the added hydrodynamic drag isn’t a concern.

Take a look at the diagram to the right. It shows not just the location of the keel cooler (at the bottom), but also the myriad pipes and valves between it and your engine.

There are advantages and disadvantages to this system. A keel cooler is simpler, since it eliminates through-hull fittings, strainers, hoses, and raw-water pumps, with their notoriously problematic impellers. On the flip side, the exposed cooling lines—even if keel-mounted—are subject to damage from underwater objects and groundings and produce unwanted hydrodynamic drag on planing hulls. Moreover, exterior corrosion can cause leaks, and accumulated fouling can degrade the tube’s heat-exchanging capability.

What is the best way to remove several drops of varnish from my fiberglass deck? B.H., via e-mail
If your decks are smooth, take a reasonably sharp putty knife and carefully pry the hardened drops off. With rough or nonskid decks, fold a paper towel into quarters, lay it on top of the varnish, and drip lacquer thinner onto the towel. This should soften the varnish enough that you can remove it with a ScotchBrite pad and some elbow grease.

I’ve ruined several putty knives with accumulated buildup from paint stripping. Any suggestions on a way to prevent this from happening in the future? R.J., via e-mail
Before beginning your job, coat both sides of your putty knife with a nonflavored, nonstick cooking spray. Then, as you continue working, clean the knife off with each pass and recoat the blade as necessary. You will find the buildup is less likely to adhere to the blade than before.

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