Installing heating on a yacht makes early and late season boating significantly more pleasant, and make using the boat in good winter weather much more attractive.
If your sailing area has plenty of marinas and you’re not making long passages, the simplest and cheapest solution by far is to use a cheap fan heater plugged into shore power. A dehumidifier is also a good option, as these are fantastic at drying out a boat and reducing condensation.
However, there are many occasions where it’s good to have heat when you can't simply plug in – at anchor, or underway, for instance. It’s important not to be tempted to use open flame devices to create heat on board, as these will release deadly poisonous carbon monoxide fumes into the cabin. All cabin heaters must have the products of combustion vented outside the vessel via a chimney or exhaust system.
A word of warning here: while many owners successfully fit their own boat heating systems, the dangers of a poor installation must never be underestimated. In particular, any kind of device within the vessel that burns oxygen has the potential to fill the accommodation space with carbon monoxide, which can quickly lead to victims falling unconscious and eventual death. Although it refers to an incident with a generator, this report by the UK’s Marine Accident Investigation Branch highlights many parallels with on board heating systems and is essential reading for anyone who installs or maintains such a system.
Solid fuel heaters on a boat
While we tend to shun solid fuel at home, there are situations in which this is the easiest and most inexpensive method of providing boat heating, especially for occasional use. The next step up from a fan heater is a bulkhead mounted charcoal heater. While these aren’t as convenient to use as a diesel fired marine central heating system, they’re a fraction of the price, can be installed in a few hours and require little maintenance. Expect an up-front cost saving of at least one third compared to the simplest warm air diesel heaters.
Charcoal heaters will put out up to around two kilowatts of dry heat, although only a limited amount of the warmth will circulate into any separate sleeping cabins. While this output is ample for most boats under around 32ft, it may not get a larger saloon really warm in seriously cold weather. However, perhaps the biggest drawback is that the heat isn’t instant – the lighting procedure only takes a minute or two, but the unit won’t reach full temperature at least half an hour. On the other hand, the heater will run all day without drawing any power from the boat’s batteries (see 8 ways to make boat batteries last longer).
For heating larger boats a more substantial solid fuel stove, with a wider diameter flue (100mm/4in) or more will kick out more heat, although a the fuel for more than a few days will take up a lot of stowage space. Charcoal and other solid fuel heaters can get very hot, so it’s worth adding a heat shield such as ceramic tiles or a metal sheet to the bulkhead, and the body of the unit must be mounted at least two inches clear of the boat’s structure. With any solid fuel heater, if the joints for the chimney are not fully sealed there is a risk of carbon monoxide escaping. A carbon monoxide alarm is therefore also a sensible and inexpensive precaution.
Diesel central heating for boats
Diesel heating is a more attractive option as it’s much more convenient to use. However, it generally takes a couple of weekends to fit if doing so yourself, or is appreciably more expensive to have professionally fitted. Many models like to be run fairly hard to prevent a build up of carbon, so there’s a balance between choosing a model that’s large enough to heat the boat in very cold weather, without being so big that it’s constantly cycling on and off. The latest models tend to be better in this respect than earlier units.
When sizing a unit, don’t bank on heating only part of the boat as this will promote condensation in other areas. On the plus side, however, the heat reaching the accommodation areas can be maximised by insulating the ducting where it runs through lockers and so on. This will appreciably increase the heat of the air at the output vents, particularly those furthest from the burner and enables the maximum amount of heat to be captured from the unit. If you’ve inherited an under-sized system in your boat, this is probably the cheapest and quickest way of boosting performance to an acceptable level.
Diesel heating units can be run on fuel from the boat’s main diesel tank. On small engines, such as most sailing yacht auxiliaries, you can T the fuel line into the engine’s fuel supply. However, there’s a disadvantage in doing so as you’re introducing more points at which air may get sucked into the engine’s fuel system. It’s therefore better to install a new standpipe in the fuel tank – most kits are supplied with this and it can be installed without draining the tank.
The exhaust can get extremely hot, particularly near the heater unit, where temperatures of more than 200C can be experienced. The exhaust must therefore be kept at least 50mm from the structure using brackets that are normally supplied in the kit. These can also be arranged to introduce a swan neck shape into the exhaust to discourage water ingress from outside. If an exhaust silencer is fitted, this must be a stainless steel marine type – not an automotive one.
Siting the heating unit on your boat
A significant advantage of pumping the heat through air ducts or radiators is that the heating unit can be positioned in an out of the way location, providing there’s easy access for maintenance. While the basic heater unit is usually very similar to those used in many automotive applications, it’s important to understand the difference between the installation requirements between these different uses.
In a road vehicle the unit is typically mounted outside of any accommodation spaces. However, even if the unit is located in an engine room or cockpit locker, on many yachts it will not be fully sealed from the living accommodation. This means that the exhaust must be gas tight and must vent overboard. In addition, the air intake for the heating air must not be in the same compartment as the exhaust. This precaution means that, in the event of an exhaust leak, fumes, including deadly carbon monoxide, won’t be pumped around the boat’s interior
Looking for more winter boat projects or inspiration? Read our features How to choose and install electric winches and 10 Great Modern Sailing Innovations.