Marine heating systems – Buyer Beware

Pete Collard

Peter Collard, technical manager for Eberspächer UK, who celebrate 40 years in the business this year, offers advice on buying a heating system.

Many owners looking to extend their season or cruise in colder climates, may contemplate fitting an on board heating system.

The popularity of the internet as a source of information, and marine discussion forums and blogs in particular, has meant that, despite some genuinely useful heater related information, there is a fair bit of misinformation too.

The controversy surrounds vehicle kits that look similar to their marine counterparts but are cheaper. This fact, as well as parts and accessories that are not pattern made, has created confusion in the market for boat owners who want to install safer ‘marine appropriate’ heating systems on their boats.


There are many differences between the two. All Eberspächer’s marine kits, for example, conform to the latest regulations and standards and are designed to be sea safe and more durable. For instance, they include extra-long double lagged exhaust systems, exhaust standoff safety brackets, fire retardant fuel systems and fuel close off valves.

In other words, the kits will endure the harsh environment found at sea. There are many other important differences such as heavy duty stainless steel brackets and fittings, gas tight flexible exhaust silencers, ducting and fittings unlikely to be seen on any type of road vehicle.


Firstly, if you are buying a new heater you should ensure it is from a genuine UK dealer.

Check what warranty is included. If the heater is new and supplied by Eberspächer then it will come with a full three year parts and labour warranty which includes travel to the boat.

There should be a comprehensive record of dispatch, sale and installation, which allows future reference to be made to enable any repair to be completed in the quickest possible time and without recourse to the customer making any payment.

Do your homework. Many new and second hand heaters sold on the internet were designed and destined for vehicle manufacturers or, if second hand, may have previously been fitted to a vehicle as a standard factory option.

It is therefore likely to feature different wiring, different switching protocol, different internal parts and so on.

The internal workings of Eberspacher’s Airtronic D2 heater

If you do buy a second hand heater for your boat, it is recommended that you price all the ancillary items first. It could be cheaper to buy a brand new full kit with three years’ parts labour and travel cover.

If you are buying parts only, be extremely careful. The part must be compatible for the heater and the job.

Finally, genuine heater parts are not just made to work; they are made to cope should something ever go wrong. Genuine parts will deal with overheating situations, harsh or extreme conditions, excessively high or low temperatures, vibration and shock. Cheap parts from internet auction sites do not always meet the same criteria, so buyer beware.

The importance of not only buying the correct system, but having it installed safely and working correctly and avoiding common errors of DIY installation such as an uneven distribution of heat, is a decision likely to save you money in the long run.


Eberspächer manufacture two different heater systems for boats. Both use combustion air and diesel fuel mixed and ignited within the heater’s internal combustion chamber to create thermal energy. The Airtronic range lends itself to more instant heat requirements by drawing in fresh or recirculated air which is heated and distributed to cabins and rooms via ducts and air outlets.  For larger boats, the Hydronic range uses a heat exchanger to transfer its thermal energy to the boat’s own internal water system and provides a more consistent heat output akin to a domestic radiator/convector based system.