Cabin heaters can transform winter sailing, and provided you've got the tools, space and time, are relatively easy to install, too. Winter is an ideal time to install a boat heater. It can make chilly mornings a thing of the past, with the promise of snug evenings aboard in a deserted anchorage. And if you've laid your boat up for the winter, stripping out cushions and equipment, it will make installing a heater a lot easier.
Choosing a heater depends on the size of your boat and your budget. It's better to have a small heater working hard than a big one ticking over that can coke up, like an idle diesel engine.
Right Angle Drill
Where to install?
If you've got the skills, tools, space and time and you want to fit a heater yourself, the prime consideration is the ducting route. Where do you want heat? Is there enough space to work? If you can, cut ducting holes through wooden panels rather than the GRP frames. Not only is drilling easier but, more importantly, you won't compromise the internal structure of the boat.
The ducting route defines where the heater can be fitted. Some heaters specifically need to be mounted horizontally or vertically. Fitting your heater close to the fuel tank and batteries will make life easier.
If you can't use the mounting board supplied, devise another to make sure the heater's location allows ducting runs without sharp angles... every 90° bend loses 5% of the heat, which is why the secret of a good heating system lies in the ducting.
Finally, think about the exhaust exit. If you stow fenders on the pushpit, siting the exhaust next to them will melt them in seconds. And remember, the exhaust needs a swan neck to prevent water entering the heater.
Boat heater installation
It is good practice to run the ducting along the upper edge of lockers to prevent it from being crushed by heavy items while sailing. Boat manufacturers expect some retro-fitted heating, as holes in the tightest places are often pre-cut at the factory. When placing the vents, always drill through from the visible side to prevent damaging the exterior. Thermostat and control wiring should be threaded through the new holes before the ducting. The dial control can be fitted anywhere the wiring will allow, but imagine being able to switch the heating on and off without having to leave the comfort of a warm bunk. Cover the ducting with a plastic bag to stop its rough edges tearing the Thermoduct insulation, then insert two sleeves of insulation over the ducting.
The fuel system
Heaters use solenoid fuel pumps so a lift pipe is needed, fitted to the tank. As the pump can't lift beyond 1m (3ft 3in), line up the lift pipe and tank, score and snap the copper pipe before gently bending it to attach to the pump, allowing two spirals in the pipe to compensate for vibration. A second pipe, running from heater to pump, needs the same treatment.
Run a protective sleeve over the stainless steel exhaust tube and bend a swan neck at the top. Drill a pilot hole in the transom and once sure it is in the right place, take the exhaust fitting outside and place it against the transom to gauge the right angle for the hole.
Using a grinding-toothed hole-cutter to prevent the gelcoat cracking, and enough marine sealant to ensure a watertight fit, bolt the skin fitting in place.
Back in the transom, attach the exhaust and cut to fit. Attach a short air inlet pipe to the heater to allow diesel combustion.
It's a lot of work, so seriously consider whether you've got the skills, tools and time to get it right.
Plan the ducting route first and keep it as straight as possible - bends lose heat. Use the right tools and, when working in confined spaces, take everything you need with you.
Turn angled skin fittings upside down and back to front to work out the correct drilling angle.
Use a vacuum cleaner while drilling into the fuel tank to minimize the debris that enters the tank.