Dave Gerr - Boat Mechanical Systems Handbook-How to Design, Install, and Recognize Proper Systems in Boats

don’t have strong natural draft like old-

fashioned wood or coal heaters, which makes

arranging the flue tricky. It’s necessary to find

the right location for the smokehead so down-

drafts and backdrafts won’t cause problems.

These independent bulkhead heaters

make good sense on boats up to about 40 feet

(12 m), assuming you can find room for them

(they can usually mount on the cabin sole or

bulkhead) and you are willing to live with

somewhat uneven heat distribution. They are

much simpler to install and maintain than

diesel-fired hot-air or hot-water heaters (see

below). Dickinson, SIG Marine, and Force 10

are three manufacturers of bulkhead heaters.

Engine-Heat Heaters

Engine-heat heaters work by simply circulat-

ing engine cooling water through them to

generate plenty of hot air in their heat

exchanger. This is then ducted throughout

the boat with a built-in blower. Since you are

using engine heat, there’s no extra fuel and

(except for some air ducts) virtually no other

systems—simple and rugged.

Again, the drawback is obvious. You get

heat only when the engine is running. For

some commercial boats, engine-heat heaters

may serve, particularly if the vessels are not

run well into the cold-weather season. Oth-

erwise, having heat only when the engine is

running is too much of a limitation.

I actually do install engine-heat heaters on

most of my motor cruisers, but for a very spe-

cific purpose: windshield defrosting. I specify

the smallest of these heaters I can find and

duct the hot air in three or four small ducts

(about 3 in. or 575 mm) to blow on the inside

of the windscreen windows in the pilothouse.

This allows you to defrost the windscreen

without having to turn on the central hot-air

heater. I’m surprised how few boats have a

heated windshield defroster system installed.

It makes a huge difference in visibility during

cold weather.

Electric defrosters available from compa-

nies like Heater Craft can also be installed

right under the windows. The advantage of

these is there’s no hose or ducting to run. The

disadvantage is the electric load.

Diesel-Fired Hot-Air Heaters

If your home has hot-air heating, it uses basi-

cally the same system as diesel-fired hot-air

heaters on boats. In a house, the furnace

burner heats hot air, which is distributed

PART FIVE: VENTILATION, AIR-CONDITIONING, AND HEATING

Figure 15-10.
Typical central
hot-air heating
system (Courtesy
Espar Products,
Inc.)