Ben Meakins installs a new silenced exhaust for his Eberspacher D1LC diesel heater
How to quieten your heater’s exhaust
Heaters are a brilliant addition to a boat – they keep the inside dry and warm, which prevents mould and mildew forming, and can extend your sailing season into the cold and wet months.
They can, however, be somewhat antisocial. Unsilenced exhausts give rise to a roar akin to an idling jet engine, which has been known to spoil the tranquillity of a peaceful anchorage. Just to walk down a pontoon in a Scottish spring or autumn is to experience what amounts to a symphony of diesel heaters.
Help is at hand, however. Heater manufacturers including Eberspächer and Webasto supply exhaust silencers which will cut the noise down considerably.
I was a little worried about the state of the exhaust on my 1992 Eberspacher D1LC diesel heater, and had never been happy with the loud roar it made at full chat, so decided that while replacing it I may as well add a silencer.
But it’s not quite as simple as you might assume. The vast majority of diesel heater exhaust silencers found online are designed for road vehicles. The marine ones are much more expensive, currently costing around £260.
But before you plump for a cheap silencer off eBay beware: vehicle silencers are designed to be mounted outside the vehicle and are not gas tight. Boat exhausts tend to be in an enclosed locker that often is linked to the living space – and the last thing you want is for exhaust fumes to be pumped in with your heated air.
Eberspächer UK’s Peter Collard has some wise words for those considering a quick, cheap deal online:
‘There is a worrying trend for people to buy vehicle heating components and fit them to their boat heaters. The vehicle components can be temptingly cheap but they may come with a heavy penalty,’ he said.
‘A commonly sought after part is a silencer for the heater’s exhaust system. Online they are commonly sold as a small stainless steel silencer box, but unfortunately most sellers don’t state that this particular silencer is not suitable for marine use.
‘A vehicle heating silencer is designed to be fitted beneath a vehicle and do a specific job – to slightly cut down the higher pitched noises associated with combustion, not totally silence the exhaust.
The silencer itself is NOT gas tight: it’s designed to go outside of a vehicle so it doesn’t need to be,’ he said. ‘If fitted in a boat the heater’s exhaust gas will be emitted into the boat while the heater is running, bringing with it deadly carbon monoxide. ‘Also, the silencer box is not thermally insulated. Again, it’s designed to go outside of a vehicle so doesn’t need to be. If fitted into a boat this component will be hot enough, when the heater is running, to cause severe injury to anyone touching it and will be hot enough to melt sails, dinghies, fenders and anything else that comes into contact with it. In certain circumstances this could lead to a fire.’ The more expensive marine silenced exhaust, Peter explained, is 2m long and includes a flexible silencer 500mm long. It’s totally gas tight and double lagged. It will be a lot healthier, safer and maybe a lot cheaper in the long run. Their new heater packages come with the silenced exhaust as standard. So, fully cognisant of the dangers of automotive silencers, I duly ordered a proper Eberspächer marine exhaust kit and set to work...
ABOVE: Gas-tight marine silencer RIGHT: Automotive silencer – dangerous for marine use
You can fit a silenced exhaust to all models of Eberspächer air heaters