The best diesel heaters for boats have seen some great improvements over the past few years. They're the most common form of heating onboard sail boats and motorboats. Full time British liveaboard for over 20 years and hardy Northerner, Fox Morgan talks through some of the most popular options for liveaboards, year round cruising and sailing at higher latitudes
Best diesel heaters for boats – This buyer’s guide was first published online in 2021 – it was revised and updated 14 Jan 2025
This Dehler 36 CWS suits easy fitment of diesel blown air heating, as it came pre marked with ducting holes and vents. There is also a secondary, shorter fuel take off from the diesel fuel tank.
I live on my boat all year round, come rain, hale, snow and heat wave. The climate I live in lends itself to having some reliable heating fitted.
I bought a second hand Taylors Paraffin heater for one of my boats, after paying for it to be professionally serviced and important bits replaced, it was still slightly less expensive than new, but not by much. Apart from the cost of buying the unit, you should factor in the cost of professional installation too.
I chose a Taylors paraffin heater for my older sailing boat because it requires no electricity at all. I have to hand pump a small tank to bring it up to pressure so that the fuel flows. I chose paraffin over the diesel option because it requires a smaller flu out of the coach roof and smaller pipework internally too. But it’s a faff compared to pressing an igniter button and having hot air pumped around the place which is what you get with a blown air heater. The downside is that they need some electricity to keep working and they’re noisy, especially for the neighbours who have to put up with the exhaust noise. To install a blown air heater on my newer sail boat is easier than the paraffin heater though as it was made with pre cut or pre marked holes for ducting under some of the furniture as it was an optional extra when the boat was new and unlike the older boat, there’s no spare bulkhead on which it could be mounted .
There’s a few second hand heaters on the market. Make sure if you do buy something second hand, that you get it professionally serviced and also when running any kind of combustible burner inside your boat ensure you have a good quality carbon monoxide detector fitted to your boat.
It can be very tempting to try one of the very low priced copies of the real deal heaters from Webasto or Eberspacher. A good number of the low-cost, often cloned diesel forced air heaters available online do not conform to UK or EU laws and regulations.
Most budget diesel forced air heaters were originally designed for trucks or motorhomes, which have different requirements and are not subjected to such a harsh corrosive environment as that found in a sea-going yacht.
Buyer beware.
I always recommend trusted heater manufacturers/brands with certified warranties and customer service backup. Buying a diesel heater intended for use in road vehicles rather than boats, or a diesel heater that does not meet UK safety standards, could pose a risk to life.
I also highly recommend that any combustible heater is professionally installed by a recognised and certified installation professional.
All of the heaters in my buyer’s guide to the best diesel heaters below have the capacity to produce and fill your cabin with carbon monoxide if incorrectly fitted or poorly maintained. The consequences can be fatal.
If you want heating you can trust then here’s my guide to the best diesel heaters for boats
I’ve divided this guide into two sections, with the best boat heaters for boats up to 38 foot and the best diesel heaters for boats over 40 foot.
The best Diesel heaters for boats up to 38 foot
Eberspacher Espar Airtronic S2 D2 L 12V 2.2kW (7500BTU) with EasyStart PRO 7 Day Timer
Specifications: heat output 2 kW, Fuel type: diesel, power: 12v or 24v, Fuel Consumption: Approx. 0.12 – 0.24 liters per hour, Dimensions (L 362 x W132 x H150 mm (approximately 14.25″ x 5.2″ x 5.9″), Weight: 2.7 kg (approximately 5.9 lbs) Noise Level: Operating noise: ~45 dB(A) at a distance of 1 meter,
Reasons you’ll like it
Simple push button start, easy to adjust temperature output, thermostatically controlled, tidy barely visible installation
Something to be aware of
This type of heater can be noisy for your neighbours, they require regular qualified maintenance
What I think of it
One of the most popular manufactures of best diesel heaters for boats , Eberspacher, has recently upgraded its Airtronic heaters, giving them a power boost mode for fast initial heating plus continuously variable temperature settings.
They also now have a fresh air mode to improve air circulation through the boat on warm days. Years of continual development has made these heaters more economical, quieter and more importantly, reliable.
Most boats that I have skippered professionally have been fitted with one of these blow air heaters. The best are the ones with fully working thermostats easy timers for on and off operation. Meaning you can go off the to the pub and set it on a timer to warm the boat shortly before your planned return. Or you can set it to go off automatically after a set amount of time, such as when you go the bed.
The wide range of controls on offer includes various panels with switches and LCDs, or there’s the latest, EasyStart Call, which allows you to operate your heater using the proprietary smartphone app.
The app turns your phone screen into a simulated control panel and transmits your selected settings to a GSM module installed in the heater.
Models include the Airtronic D2 and S2 D2L (<32ft LOA), D4+ and M2 D4L (26-39ft), D5 (36-49ft) and the D8LC (49-62ft).
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Webasto Air Top 2000 STC 12v Marine diesel boat heater kit
Specifications: Output: Max 2.2 kW Min 0.9 kW, Fuel Type:Diesel (can be connected to the boat’s existing fuel tank), Voltage Supply: 12V DC, Power Consumption (Electrical): 4.0 A (on startup) Continuous consumption: 1.5 A (during operation), Fuel Consumption: Maximum consumption: 0.22 l/h Minimum consumption: 0.10 l/h (at minimum heating power), Dimensions Length: 365 mm (14.4 inches) Width: 120 mm (4.7 inches) Height: 155 mm (6.1 inches), Weight: 2.7 kg (5.95 lbs), Noise Level: 48 dB(A) at 1 meter
Reasons you’ll like it
Simple push button start, easy to adjust temperature output, thermostatically controlled, tidy barely visible installation
Something to be aware of
This type of heater can be noisy for your neighbours, they require regular qualified maintenance
What I think of it
Webasto’s steplessly modulated heating systems are renowned for their high build quality, performance and reliability.
The range features numerous safety devices and procedures, including flame detection and exhaust heat sensing, to ensure safe operation.
The smaller and less sophisticated model is its Airtop 2000STC, a 2kW heater that offers up to two outlets, thermostatic controls, external temperature sensor, air intake silencer and low-noise fuel pump.
The new MultiControl digital timer/temp controller offers instant access to functions plus a quick start button and is sealed against water ingress.
I’ve skippered a fair few boats and invariably, if they’re not fitted with an Eberspacher, they’re fitted with a Webasto. The two are very similar to use and really the choices of which to go with depends on your local service centres and availability of spares in your territory/location.
Webasto are known as one of the leading manufacturers of best diesel heaters for boats and appear much the same as Eberspacher heaters… but they are different and have small differences.
For larger yachts there’s the high-output, multi-mode Airtop Evo 3900 (<40ft) or 50 (<50ft).
Both are powerful, yet quiet and economical and can be controlled using a MultiControl, a TeleStart wireless remote pad or via a mobile phone app using its ThermoCall system.
The temperature is regulated using intelligent blower control whereby the heater output and fan controls are separately sensed to reduce power and fuel consumption.
The Evo series has also been upgraded with ECO mode for reduced electrical power consumption, Boost mode for maximum output and Ventilation mode to provide fresh air to the cabins on a hot day.
Wallas 22GB Coastal Kit
Specifications: Fuel Type: Diesel, Voltage: 12V DC, Power Output: Max 2.4 kW, Min 1.0 kW, Fuel Consumption:Max 0.24 litres per hour, Min 0.10 litres per hour, Dimensions Length: 458 mm (18 inches) Width: 210 mm (8.3 inches) Height: 168 mm (6.6 inches), Weight: Approx. 5.5 kg (12.1 lbs), Noise Level: Approximate noise level: 47-50 dB
Reasons you’ll like it
Simple push button start, easy to adjust temperature output, thermostatically controlled, tidy barely visible installation
Something to be aware of
This type of heater can be noisy for your neighbours, they require regular qualified maintenance
What I think of it
Wallas recently updated its 2.2kW (22GB) and 3.2kW (30GB) Nautic models by changing their blower motors to brushless types.
The result is more power and output capacity, allowing the boat to heat up quickly, efficiently and quietly.
Its new laminar flow burner offers low emissions of CO2 and NOx, and is designed to work with blended bio-diesel.
Renewable materials are used in its construction, although it retains high-grade aluminium components where necessary.
The new control panel offers smooth PI-controlled thermostat adjustment and two-step air boost protection against accidental operation.
Like most systems now, Planar heaters can be controlled via your phone
Autoterm BOAT Diesel Heater 2 kW Medium
Specifications: Fuel Type: Diesel, Voltage: 12V DC or 24V DC (depending on configuration) Heating Output: Max 2.2 kW Min 1.0 kW Fuel Consumption: Maximum fuel consumption: 0.24 liters per hour (at full power) Minimum fuel consumption: 0.10 liters per hour (at low power) Dimensions: Length: 360 mm (14.2 inches) Width: 130 mm (5.1 inches) Height: 150 mm (5.9 inches), Weight: Approx. 3.5 kg (7.7 lbs), Noise Level: 40-45 dB(A) at 1 meter
Reasons you’ll like it
Simple push button start, easy to adjust temperature output, barely visible installation, spares are easy to find and low cost
Something to be aware of
This type of heater can be noisy for your neighbours, they require regular maintenance
What I think of it
New kid on the block, Latvian-built Planar heaters appear to be a genuine compromise between cost and quality, although there seems to be little difference in the latter to the higher-priced brands.
Planar’s UK distributor is currently small, yet it holds a full range of spare parts (unlike many of the cheaper Chinese models) and the reviews on its service have so far been excellent.
Its Autoterm Air marine range comprises a 2kW and 4kW heater; however, larger units can be made specifically to suit.
The standard kit comes with a basic rotary control panel offering stop/start, capacity and air temp control and LED indication of heater status.
The next level has an additional seven-day timer, ventilation mode and an LCD for temperature indication.
Finally, there’s a GSM modem option with smartphone app for remote operation via the mobile phone network.
This offers all the features of the more advanced LCD control panel, only on your smartphone.
Refleks Stove Heater Refleks 11032-66M heater
Specifications: Fuel Type: Diesel, Voltage: None (This is a gravity-fed system, so it doesn’t require an electrical supply for operation), Heating Output: Max 3.0 kW Min 1.0 kW, Fuel Consumption: Max 0.25 litres per hour, Min 0.10 litres per hour, Dimensions: Height: 325 mm (12.8 inches) Width: 310 mm (12.2 inches) Depth: 365 mm (14.4 inches) Weight: Approx. 9.5 kg (20.9 lbs)
Reasons you’ll like it
It’s is a very simple heater and easy to maintain, silent running, requires no electricity
Something to be aware of
lighting it takes a few minutes, you will need to cut a hole in your roof for the flu, severe/adverse weather can cause a bit of blowback
What I think of it
The Refleks Danish made stoves are popular with more traditional year round cruisers. Seen in working boats, fishing boats and a wide array of sail boats and traditional motor cruisers, the Refleks diesel heaters are king of the cold. They’re sturdy drip fed units that radiate heat rather than blow it around.
The larger Refleks stove heater models have additional internal pipework that allows further radiator heat or hot water heating. This small unit is the most basic and most budget friendly though and considered practically bomb proof.
You’ll see Refleks heaters on board many boats, quietly kicking heat out. You’ll see a larger model on board Skip Novaks Vinson of Antartica, but you’ll also see a tiny model, such as this one I’ve shown here in just about every boatman cabin on the barges working the canals of Netherlands and Holland. I do rather like this little video about how to start one by Sail Life on YouTube
My friends with a Jeanneau Sunshine 38 had one of these and I spent some lovely evenings sitting by it in the depths of a British winter. Only occasionally did we get a little pop of blowback when the wind was howling. I think that’s remedied with a better baffled flu top cowl.
The advantage of the drip fed heaters is that you don’t get the loud exhaust noise associated with blown air diesel heaters.
Total heat output: 1.6 kW (1400 kcal/h)
Fuel consumption: min. 0.12 l/h
Fuel consumption: max. 0.30 l/h
This one is for area volume sizes of approx. 14 – 23 Cu. Mtrs.
for more info on Refleks heaters go to the manufacturer site
Taylors Paraffin Heater 079K
Specifications: Fuel Type: Paraffin (Kerosene), Power Output: 1.5-3.5 kW, Fuel Consumption: Max: 0.3 litres per hour, Min: 0.1 litres per hour, Dimensions: Height: 430 mm (17 inches)Width: 270 mm (10.6 inches) Depth: 300 mm (12 inches)
Reasons you’ll like it
Quiet when in use, radiates heat, simple and easy to maintain, requires no electricity, will last decades with minimal maintenance and can be used for days/weeks at a time without need for any specialist expertise.
Something to be aware of
You will need to fit a flu through the top of your boat, you will need a bulkhead to mount it on, you will need to add a heat proof back plate, it requires a little effort to light it
What I think of it
The classic looking heater comes in two forms, one uses diesel (see below) and one uses paraffin or kerosene. There’s a few little differences between the two. Primarily there’s the fuel delivery.
The Paraffin heater uses a small tank that is hand pumped up to pressure to keep the fuel flowing. No electricity is required. The other difference between the two versions of the same heater is that the paraffin heater uses a smaller diameter flu. This allows a smaller hole in the cabin top.
The Taylors heater is a superbly simple heater for boats. Fitted to a bulkhead the heater radiates heat rather than pumps hot air around ducting. As such it is virtually silent running.
Front opening door gives access for lighting it, maintenance or adjustment and it comes with the tank, pressure gauge and hand pump built in.
Externally vented and bulkhead mounted, through-deck fitting flue sections are also supplied.
Available in a brass or a Stainless Steel finish.
An excellent choice for anyone wanting to live aboard or use their boat year round. This model suits a smaller boat up to 38 foot.
You can buy spares for them from Blakes Taylor based in the UK near Southampton
Taylors Diesel Heater 079D
Specifications: Fuel Type: Diesel, Voltage: 12V DC, Power Output: 3.0 kW, Fuel Consumption: Maximum: 0.35 litres per hour, Minimum: 0.15 litres per hour, Dimensions: Length: 500 mm (19.7 inches) Width: 380 mm (15 inches) Height: 330 mm (13 inches) Weight: Approximately 14 kg (30.9 lbs) Materials: Stainless Steel
Reasons you’ll like it
Quiet when in use, radiates heat, simple and easy to maintain, requires no electricity
Something to be aware of
You will need to fit a flu through the top of your boat, it requires a little effort to light it
What I think of it
Fuelled by red or clear diesel, fed from from its own gravity tank – Header tank version – or pumped direct from the boat’s supply – main fuel tank version.
It is a superbly simple heater for boats. Fitted to a bulkhead the heater radiates heat rather than pumps hot air around ducting. As a gravity fed unit this is virtually silent running.
Front opening door gives access for maintenance or adjustment, Supplied with a 1.5 gallon tank, a safety on/off fuel control valve, in-line fuel filter, pipe work and fittings for installation,
Externally vented and bulkhead mounted, through-deck fitting flue sections are also supplied.
Available in a brass or a Stainless Steel finish.
An excellent choice for anyone wanting to live aboard or use their boat year round. This model suits a smaller boat up to 38 foot.
As Taylors are no longer making these due to a loss of engineering skills in the UK, they do still provide spares, so, as such you can just about build your own from the spares. Ebay can be a good source for second hand Taylors heaters.
Blakes Taylor based in the UK near Southampton
The best Diesel heaters for boats over 40 foot
A digital timer offers instant access to functions
Webasto Air Top Evo 3900 Marine Heater
Specifications: Heating Output: max 3.9 kW min 1.6kW, Fuel Type: Diesel (can be connected to the boat’s main fuel tank), Voltage Supply: 12V or 24V DC (depending on model), Power Consumption (Electrical): Start-up: 8 A (initial surge), Operation: Approx. 2.5 A at 12V, 1.25 A at 24V, Fuel Consumption: Maximum consumption: 0.38 l/h, Minimum consumption: 0.15 l/h, Dimensions Length: 356 mm (14 inches) Width: 122 mm (4.8 inches) Height: 144 mm (5.7 inches), Weight: Approx. 4.5 kg (9.9 lbs), Noise Level: Operating noise: ~45 dB(A) at a distance of 1 meter
Reasons you’ll like it
Simple push button start, easy to adjust temperature output, thermostatically controlled, tidy barely visible installation
Something to be aware of
This type of heater can be noisy for your neighbours, they require regular maintenance
What I think of it
Webasto’s steplessly modulated heating systems are renowned for their high build quality, performance and reliability.
The range features numerous safety devices and procedures, including flame detection and exhaust heat sensing, to ensure safe operation.
The new MultiControl digital timer/temp controller offers instant access to functions plus a quick start button and is sealed against water ingress.
ECO mode for reduced electric consumption, power mode PLUS for +10% more heat output (from 3,500 W to 3,900 W) and ventilation mode to supply fresh, cold air to the interior on hot days.
It is supplied with a universal marine kit which includes copper fuel piping and appropriate connections, fittings for installation and rotary controller. Ducting or Outlets are sold separately as an added extra.
Fuel Consumption Control Range: 0,17 – 0,42 l/h -Nominal power consumption control range: 15-36W –
Weight: 5.9kg -L x W x H: 425 x 148 x 148 mm
Webasto Air Top EVO 40 4kW 12v Marine Heater Kit with MultiControl HD 7-Day Timer
Specifications: Heating Output: max 3.9 kW min 1.6kW, Fuel Type: Diesel (can be connected to the boat’s main fuel tank), Voltage Supply: 12V or 24V DC (depending on model), Power Consumption (Electrical): Start-up: 8 A (initial surge), Operation: Approx. 2.5 A at 12V, 1.25 A at 24V, Fuel Consumption: Maximum consumption: 0.38 l/h, Minimum consumption: 0.15 l/h, Dimensions Length: 356 mm (14 inches) Width: 122 mm (4.8 inches) Height: 144 mm (5.7 inches), Weight: Approx. 4.5 kg (9.9 lbs), Noise Level: Operating noise: ~45 dB(A) at a distance of 1 meter
Reasons you’ll like it
Simple push button start, easy to adjust temperature output, thermostatically controlled, tidy barely visible installation
Something to be aware of
This type of heater can be noisy for your neighbours, they require regular maintenance
What I think of it
The Webasto Air Top EVO 40 is compact, quiet, and economical heater requiring from 0.18 to 0.43 litres of diesel per hour.
Suitable and trusted for many types of marine installations and certified for installation in passenger areas and in proximity to dangerous substances.
This Webasto Air Top EVO 40 heater comes with a complete installation kit to install into your boat. This components option can also be viewed perhaps as a starter kit, supplied with basic electronic temperature control. This kit does not include ducting or air outlets – please see our range of additional ducting outlets and digital controllers to enable a truly bespoke and cost-effective Marine solution.
Marine 12volt 4.0kw kit Contents:
• Webasto Air Top EVO40 self regulating 12 volt air heater with
• MultiControl HD 7-Day Timer with On-board diagnostics
• All electrical harnesses and connections
• 1.8m Stainless steel exhaust silencer supplied with lagging insulation (measured lengths of 24mm stainless steel exhaust pipe are available if required)
• Copper Fuel pipe system, complete with fuel metering pump
• 1 x Fuel Stand Pipe
• All necessary clips and screws for this installation included
• Comprehensive installation manual
• Stainless steel Heater mount bracket
• Stainless steel exhaust hull skin fitting
• Webasto Air Top EVO40 24 months warranty
Eberspacher Airtronic M2 D4 L 4KW 12v Diesel 2 Outlet Marine inc Easy Start PRO
Specifications: Fuel Type: Diesel (runs off the boat’s main diesel fuel tank), Voltage: 12V DC, Power Output: 4.0 kW, Fuel Consumption: Max 0.44 liters per hour (at full power) Min 0.1 liters per hour (at low power), Dimensions: Length: 420 mm (16.5 inches) Width: 170 mm (6.7 inches) Height: 300 mm (11.8 inches) Weight: Approx. 6.2 kg (13.6 lbs), Noise Level: Operation noise: Approx. 47-50 dB(A) at 1 meter
Reasons you’ll like it
Simple push button start, easy to adjust temperature output, thermostatically controlled, tidy barely visible installation
Something to be aware of
This type of heater can be noisy for your neighbours, they require regular professional maintenance
What I think of it
One of the best known makes of marine heaters, Eberspacher, has recently upgraded its Airtronic heaters, giving them a power boost mode for fast initial heating plus continuously variable temperature settings.
They also now have a fresh air mode to improve air circulation through the boat on warm days.
Years of continual development has made these heaters more economical, quieter and more importantly, reliable.
The wide range of controls on offer includes various panels with switches and LCDs, or there’s the latest, EasyStart Call, which allows you to operate your heater using the proprietary smartphone app.
The app turns your phone screen into a simulated control panel and transmits your selected settings to a GSM module installed in the heater.
Models include the Airtronic D2 and S2 D2L (<32ft LOA), D4+ and M2 D4L (26-39ft), D5 (36-49ft) and the D8LC (49-62ft).
Buy it now from heater parts direct
Eberspacher Hydronic S3 HS3 Universal 5kW 17000BTU Vehicle Water Heating Kit including Easy Start PRO 12v
Specifications: Fuel Type: Diesel, Voltage: 12V DC, Heating Power: 5.0kW, Heat Output in BTU: 17,000 BTU (approx.), Fuel Consumption: Maximum Fuel Consumption: 0.50 litres per hour (at full output), Minimum Fuel Consumption: 0.13 litres per hour (at low output), Water Temperature Control: Operating Temperature: 30°C to 85°C (86°F to 185°F), Maximum Operating Pressure: 2.5 bar (36 psi), Airflow (for cabin heating):Maximum Airflow: 300 m³/h (cubic meters per hour) for air distribution (varies depending on the system and air ducts used) Dimensions: Heater Unit (Main Heater): Length: 300 mm (11.8 inches) Width: 240 mm (9.4 inches) Height: 160 mm (6.3 inches) Weight: Approx. 5.5 kg (12.1 lbs)
Reasons you’ll like it
Simple push button start, easy to adjust temperature output, thermostatically controlled, heats water as well as heating radiators and heat exchangers for warm air ducted heating
Something to be aware of
This type of heater requires radiators/heat exchangers so you’ll need space to fit those where they will be most effective, given the additional complexity and weight associated with a wet heating system, this suits a larger vessel.
What I think of it
This is the Daddy of consumer heating systems. Not only do you feel toasty and warm, you get hot water too. Fancy a shower to warm up, then sure, go ahead (within the confines of your water rations)
Yeah, I love this heating system. Obviously it’s at the higher end of the price scale from this group of heaters I’ve presented in this buyers guide. But this can kick some serious heat out for larger boats. It also has scope to allow heated towel rails and radiators that give a different type of heat to blown air. It can still be used for blown air too, through a heat exchanger, so if you like that sort of thing in your wet locker to dry your wet foul wet gear then it has you covered. I’ve generally only seen this on boats over 45 feet, but I’m sure it could be accommodated on smaller boats.
Diesel fired water heater with 5 kW heating power, for cabin interior saloon heating and engine pre-heating.
The Hydronic can heat domestic hot water if coupled with a plate heat exchanger, hydroplate or calorifier.
The kit includes
Eberspacher Espar Hydronic S3 D5E CS
Water pump and fuel pump
Easy Start Pro Controller with 7-day timing and altitude switching
Heater wiring harness and electrical accessories
Mounting bracket and fixing bolts
Features:
Stepless modulated heating from 1.3kW up to 5kW depending on requirement.
dimensions: 215 x 91 x 144 mm.
Silent running fuel pump
The Hydronic S3 Economy has a service life of 3000 hours. That’s just over 8 hours a day for 365 days of the year!
Buy upgrade kit from Butler Tecknik
Buy complete kit from Butler Tecknik
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FIREANGEL FA3820-EUX10 BATTERY STANDALONE CARBON MONOXIDE ALARM
Every boat should be fitted with at least one carbon monoxide alarm.
The current range of carbon monoxide alarms for boats have a long 10 year battery life and have a test button. Most of the carbon monoxide detectors that give a readout on a screen built in are intended for RV’s and camper vans and usually aren’t sold for boats.
Some carbon monoxide detectors are also smoke detectors.
I have this FireAngel fitted to both of my boats.
Duncan Kent says…
Common issues are incorrectly designed exhausts, corrosive steel clips, screws and brackets, plastic fuel lines and filters, and non-watertight casings.
Some really cheap models lack thermal sensors, overheat alarms and shutdown modes, thereby presenting a very real risk of an onboard fire should the heat outlet accidentally be covered by a carelessly placed sail bag or drooping sleeping bag.
There’s also the possibility of carbon monoxide entering the boat if a fender is left dangling over the exhaust while the heater is running, or if the silencer is of poor quality with crimped, rather than welded seams.
All these are very typical scenarios found on a cruising yacht and highlight the need for the appropriate, built-in safety devices listed in the regulations.
Recent advances in diesel forced air heaters
As with most marine equipment, heating systems have been subject to gradual improvement over the past decade, both in regard to technical features and from a safety point of view.
Many are also now more economical on fuel and efficient on output, and the introduction of brushless fan motors has resulted in them using less electrical power and running much more quietly.
New glow ‘pins’ rather than the older style glow ‘plugs’ have greatly improved fuel burn efficiency too and gone a long way towards eliminating ‘coking up’.
Many recent diesel heater models now have a boost function just to pre-warm the boat and an eco-setting in which it just ticks over enough to retain the temperature within a narrow range.
There has also been a good deal of improvement in the controls.
In the past they’ve been simple electro-mechanical devices with either a rheostat or multi-way switch to select the temperature range.
Then along came more accurate controls with LCD displays and built-in seven-day timers.
Now, there are wireless remotes on offer and you can even control heaters by mobile app or online, so that you can switch the heater on when you’re a few miles away and climb aboard a toasty boat whatever the weather.
How much will a diesel forced air heater cost me?
It’s important to work out what you need for your installation before attempting to compare prices.
Most kits come with enough bits for a single outlet and the minimal amount of ducting. So, if you want two outlets, you’ll need to measure carefully and price it in, along with a grill and a T-piece connector (£60).
Many owners now fit silencers to the fresh air intake as well, to quieten the ‘roar’ heard with older models, plus anti- vibration rubber mounts to lessen the sound of the fuel pump are also available.
Continues below…
The cost can increase if you want a fancy controller, too.
They usually come with just an analogue rotary-type knob with an LED or two to indicate operation status.
While this might suit some, others may want a remote panel with an LCD to show what’s going on (£150- £200), or even control via their phone.
Don’t be fooled by the ‘free’ app though, it’ll only work if the heater is connected to the GSM network, and that involves buying a modem and a SIM card (£200-£300, plus around £7.50/ month for the SIM).
If you get an advanced control box it’s worth fitting a temperature sensor. Finally, check how long the standard control cable is, as an extension can sometimes mean it’s cheaper and easier to opt for a wireless remote (£150).
Marine heater safety
Many of these heaters are designed for vehicles and don’t always list a specific marine kit.
Check the kit contains enough lagging to double-lag the exhaust and make sure the exhaust outlet is stainless or bronze and angled up to allow for a swan-neck in the pipe to eliminate back-feed of water.
It is also worth double checking the kit is marine specific.
Automotive heaters are designed to be fitted externally, so do not require the same standard of air-tightness on the joins around the exhaust and on the welds around the silencer.
Similarly, metal fittings may be galvanised rather than stainless steel, and vulnerable to rust, and fuel lines not of the same specification.
The critical safety issue is that of carbon monoxide.
A properly installed heating system will run without issue, but as we’ve seen too often, an exhaust leak or other fault can be fatal.
All boats should have a CO alarm anyway, but check yours is in date and working.