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Ask an expert: Trawler Q&A: Heat exchangers, explained; fighting mold and mildew; NOAA Custom Chart contributions and more

Your technical questions answered by some of the most experienced trawler minds afloat.

Automobile engines are (mostly) water-cooled, but also have a radiator to cool the liquid coolant. Boats are also (mostly) water-cooled, but they have heat exchangers that use seawater to cool the liquid coolant. It seems to me that anytime seawater is introduced into a system, trouble is not far behind. Why don’t boats have radiators like cars do? —Lisa Olson

You are not the first person to ask that question. And interestingly, there are a few boats out there with air-cooled engines. The amphibious World War II DUWK boats and airplane-propellered swamp boats come to mind. The main problem comes with supplying enough air to keep the engine cool. That is not an issue if you have a giant fan like a swamp boat does, but a typical trawler would require similar air movement down to the hot (and getting hotter) radiator and then back out. This air would need to be forced, loudly, through large ducts since the boat’s speed would not generate the kind of flow a car generates. You are correct that introducing seawater into engine systems is problematic. Unfortunately, it is still the better engineering solution in most cases. —Max Parker, Zimmerman Marine

I’m thinking about spraying the electrical connections in my electrical panel and any exposed connections, like on the starter, with Boeshield T-9 to prevent corrosion and drive out any moisture. What do you think? Also, I run a dehumidifier in my engine room and in the salon. I try to keep the humidity below 50 percent to stop mold and mildew. Is this a good practice? I’m concerned about the nice woodwork drying out and cracking. —Dave Mellis

Spraying an oil or demoisturizer on exterior connections such as power cord outlets or plugs is fine, but be sure to wipe up drips. However, I have never sprayed any compound into my sealed electrical panel or cabinet because of the heat generated in the enclosed space, and because such compounds attract dust, dirt and lint. If you are worried about the connections, open the door once a year and check every connection for tightness, corrosion, frayed wires or broken insulation. There should not be any moisture seeping into the electrical panel unless you have a leak that needs fixing.

I’m not sure why you would need a dehumidifier in the engine room. Running the engine at the dock will heat up the hardware and keep the space dry between regular trips. In the salon, determine how much humidity is drawn out and set the unit accordingly. In Florida, we generally run the air conditioning all the time to keep the interior dry, but opening hatches on a breezy day at the dock is the best way to have clean, dry, fresh air circulating through the lazarette, bilge and interior. You also could try running a small circulating fan in the salon and a forward stateroom to keep air moving throughout the interior. On hot days, I also open the zippers on my flybridge enclosure to keep the area from becoming a heat trap.

—Peter Frederiksen

I enjoyed Bob Sweet’s article “Help Wanted: The accuracy of future charts depends on all of us using NOAA Custom Chart today” [October 2021]. It was a very good piece but did not say how we could provide the help needed. If there is something I can contribute as a boater, I’d like to know how. —Alan Darelius

The whole idea is to get everyone involved. With the National Oceanic and Atmospheric Administration moving to eliminate paper charts, the NOAA Custom Chart (NCC) online application is their answer to those who still want printed charts—as we all should! Using NCC, you can create a PDF of a chart by using the vector chart database. Presently, these charts fall short of what most of us would consider adequate. The solution is to press NOAA to evolve NCC until we get charts we can use, before our existing charts go away.

Start by accessing NCC at and then go to the feedback icon (the fifth icon down on the left side of the screen). Even if you do not try to create your own charts, you can comment. NOAA is required to respond and log the comments.

If you choose to create a chart, the first icon offers instructions. The second icon sets the parameters, such as paper size, orientation, chart scale and depth contours. The third icon lets you position the center of your chart and move it around. The fourth icon begins the download process. The finished PDF will appear in a separate tab on your browser.

Right now, the charts lack proper labels, including for navigation aids and landmarks. The charts also lack details on land. —Bob Sweet

I can relate to the tip submitted by Robert Neefus in the October 2021 issue on using LanoCote on mast step machine screws. That somewhat approaches an application I’ve been using for about 24 years that hasn’t failed yet. On haul out, I slather on a thick coat of lanolin over all running gear, props, struts, rudder, trim tabs, thru-hull fittings and even a light coating across my underwater lights. The stuff comes in a tub and is about the consistency of peanut butter. It prevents growth of any kind, even up here in New York’s Great South Bay. I swear by it. So far, the only person that doesn’t agree is the yard guy that had to re-tighten the props after I finished. Apparently, the stuff doubles as a good skin moisturizer. Win-win. —Capt. David Mahler