Opinions on Webasto diesel heaters

[Hunter1]

Hi folks, 

 

I plan to have a diesel heater fitted to the back of the boat for an extra boost in the winter. My local yard likes to install Webasto. 

 

Slightly concerned after searching "Webasto" on here that there were approx. a billion posts about issues with them! 

 

The mechanic suggested I'd need to have a duct with vents installed along the boat if I wanted the heat to pass any bulkheads. Are the heaters really that weak? I have an open corridor down the boat, and hope for the heater to take the edge of the bathroom in the winter (with is about halfway down the boat).

 

I've heard you can get a version with a SIM, which allows you to turn it on remotely. Has anyone got any experience with this? The mechanic at the yard looked a bit alarmed by the suggestion - but my dream of coming back to a not-freezing boat after a night out in the winter is strong! Also being able to control it remotely from my bed would be marvellous. 

 

Thoughts, suggestions, experiences welcome. 

 

Note: I'm not intending to use it as a replacement for my stove (which is at the very front of the boat) - just to heat up the back end to help reduce damp at that end in the winter, and speed up warming the boat through on winter mornings when I need to brave the shower! 

[mrsmelly]

I have had webasto on two of my full time liveaboard boats. They are great if installed correctly with lots of rads. Run them hot for as long as possible. And what many people do not do is remove and service EVERY year. I had two on my last boat so one was in commision and one kept as spare and whilst one was being serviced there was always one connected. Run them for at least an hour each time and run them once a week for an hour in the summer to keep them happy. 

Oh and instal them with shut of valves on the in out pipes to make it a doddle to remove and service with virtualy zero coolant loss. 

[junior]

Can't comment on a Websto, but I have a Autoterm (used to be Planar)  diesel heater that was fitted 2 winters ago and I'm very happy. Like you, I fitted it as a secondary heating source as I already have 2 x solid fuel stoves on the boat. 

 

There will be hundreds of thousands of Websstos fitted in boats, lorries and campervans all over the world that work absolutely fine. Nobody ever posts on the internet about their fully working Webssto, so of course when you do a search you'll only find negative stuff. You'd get the same result for Autoterm, Eberspacher etc...

 

I'm not an expert on Diesel heaters, but I did loads of research when I was trying to decide what was right for me. My conclusion is that the system is only as good as the install and components used. The units themselves should all function to a certain standard, and if looked after, serviced and not abused should rarely go wrong. 

 

For example, I follow the Autoterm Facebook group. People often post that their heater has stopped working or is throwing up fault codes. The results almost always turn out to be incorrectly fitted fuel pick ups or fuel filters , or things like bends in the ducting being too tight or ducting hose being of the wrong diameter. Stuff like that, rather than a faulty heater unit needing replacing. 

 

In terms of ducting and bulkheads etc, the heaters themselves (or the exhausts) can be quite noisy. You wouldn't really want the heater fitted in the room you want to heat. Much better to mount it in an engine room or cupboard and then duct the heat to where you want it. You also need to mount it reasonably close to where your exhaust outlet will be as you don't want a long exhaust run. 

 

Someone will be along soon to quote BSS rules and regs and fill the thread with doom and gloom about cheap Chinese Diesel heaters, I'll leave that to them. Just make sure your exhaust is a proper marine exhaust and not one designed for a campervan, that where most of the problems (death) occurs.

[Tony Brooks]

33 minutes ago, Hunter1 said:

Slightly concerned after searching "Webasto" on here that there were approx. a billion posts about issues with them! 

 

Look at the dates of posting, things seem to have improved considerably since low sulphur diesel was mandated.

 

34 minutes ago, Hunter1 said:

The mechanic suggested I'd need to have a duct with vents installed along the boat

 

That suggests that you, or he, are thinking of fitting a hot air Webasto which tended to be more reliable than the hot water ones Mrsmelly was talking about.

 

All our hot air Webastos on the Thames hire fleet were ducted to ensure hot air was supplied to every part of the boat not much above floor level.

 

38 minutes ago, Hunter1 said:

I have an open corridor down the boat, and hope for the heater to take the edge of the bathroom in the winter (with is about halfway down the boat

 

and how do you suppose a blast of hot air from the back of the boat up the corridor will turn through 90 degrees to get into the bathroom, by the time it got there the hot air is likely to be running along the roof.

 

 

The talk of a duct MIGHT be to hide central heating pipes from a wet Webasto, you need to clarify.

[cuthound]

23 minutes ago, mrsmelly said:

I have had webasto on two of my full time liveaboard boats. They are great if installed correctly with lots of rads. Run them hot for as long as possible. And what many people do not do is remove and service EVERY year. I had two on my last boat so one was in commision and one kept as spare and whilst one was being serviced there was always one connected. Run them for at least an hour each time and run them once a week for an hour in the summer to keep them happy. 

Oh and instal them with shut of valves on the in out pipes to make it a doddle to remove and service with virtualy zero coolant loss. 

 

When I bought my boat it was 7 years old and the Webasto had been serviced every year (I got a file with all receipts in it when I got the boat).

 

My surveyor told me what you suggest. Run it hard for an hour then turn it off to let it cool down. This burns off the carbon deposits and negates the need for annual servicing.Don't run it on part load and don't get it serviced until it obviously needs it.

 

The boat is now 19 years old and the Webasto works perfectly. It hasn't been serviced for 12 years now.

[Jen-in-Wellies]

18 minutes ago, Tony Brooks said:

Look at the dates of posting, things seem to have improved considerably since low sulphur diesel was mandated.

This. They were designed for road vehicles, burning road diesel. The red you got on the cut used to be much higher sulphur content than now. Since it went to what we have now, essentially road diesel with red dye, Webasto, Planar, Eberspacher, Chinese etc heaters seem much happier and don't fail as often. 

[mrsmelly]

22 minutes ago, cuthound said:

 

When I bought my boat it was 7 years old and the Webasto had been serviced every year (I got a file with all receipts in it when I got the boat).

 

My surveyor told me what you suggest. Run it hard for an hour then turn it off to let it cool down. This burns off the carbon deposits and negates the need for annual servicing.Don't run it on part load and don't get it serviced until it obviously needs it.

 

The boat is now 19 years old and the Webasto works perfectly. It hasn't been serviced for 12 years now.

Your tight thats all 🤣 In this boring house I also get the boiler serviced every year 😜 

[MtB]

9 hours ago, mrsmelly said:

Your tight thats all 🤣 In this boring house I also get the boiler serviced every year 😜 

 

Money to burn, eh?!

 

I service my boiler here in the hovel every ten years, whether it needs it or not. 

 

 

[mrsmelly]

16 minutes ago, MtB said:

 

Money to burn, eh?!

 

I service my boiler here in the hovel every ten years, whether it needs it or not. 

 

 

No insurance company will ever catch me out if we have a fire by saying I hadnt serviced boiler. AND 7 year guarantee only valid if yearly serviced 

I also have all the Heta and Fensa bullshit so when I sold this house the solicitors bullshit questions were disposed of 😜 

[matty40s]

11 hours ago, Tony Brooks said:

 

Look at the dates of posting, things seem to have improved considerably since low sulphur diesel was mandated.

Not entirely....

There have been a lot more problems with fuel pumps on systems that are not used regularly....not a difficult job to fix with an external Webasto fuel pump, but slightly more involved with the internal eberspacher pump.

[Hunter1]

On 06/05/2026 at 11:16, mrsmelly said:

I have had webasto on two of my full time liveaboard boats. They are great if installed correctly with lots of rads. Run them hot for as long as possible. And what many people do not do is remove and service EVERY year. I had two on my last boat so one was in commision and one kept as spare and whilst one was being serviced there was always one connected. Run them for at least an hour each time and run them once a week for an hour in the summer to keep them happy. 

Oh and instal them with shut of valves on the in out pipes to make it a doddle to remove and service with virtualy zero coolant loss. 

 

Thanks mrsmelly - that's great to hear. The guys at my yard are really good, so I know they'll install it correctly. What is involved with the service? It sounds like you send it off / drop it off somewhere (re: keeping a spare).

 

I'm just having an air heater, no radiators... It's really just to top up the back end / warm up the bathroom. Also a full system with rads is out of budget!

 

On 06/05/2026 at 11:30, junior said:

There will be hundreds of thousands of Websstos fitted in boats, lorries and campervans all over the world that work absolutely fine. Nobody ever posts on the internet about their fully working Webssto, so of course when you do a search you'll only find negative stuff. You'd get the same result for Autoterm, Eberspacher etc...

 

Hehe, very good point!!

 

On 06/05/2026 at 11:30, junior said:

My conclusion is that the system is only as good as the install and components used. The units themselves should all function to a certain standard, and if looked after, serviced and not abused should rarely go wrong. 

 

For example, I follow the Autoterm Facebook group. People often post that their heater has stopped working or is throwing up fault codes. The results almost always turn out to be incorrectly fitted fuel pick ups or fuel filters , or things like bends in the ducting being too tight or ducting hose being of the wrong diameter. Stuff like that, rather than a faulty heater unit needing replacing. 

 

This is great advice, thanks. 

 

On 06/05/2026 at 11:30, junior said:

In terms of ducting and bulkheads etc, the heaters themselves (or the exhausts) can be quite noisy. You wouldn't really want the heater fitted in the room you want to heat. Much better to mount it in an engine room or cupboard and then duct the heat to where you want it. You also need to mount it reasonably close to where your exhaust outlet will be as you don't want a long exhaust run. 

 

Someone will be along soon to quote BSS rules and regs and fill the thread with doom and gloom about cheap Chinese Diesel heaters, I'll leave that to them. Just make sure your exhaust is a proper marine exhaust and not one designed for a campervan, that where most of the problems (death) occurs.

 

I've got a cruiser stern, so lots of space in the engine bay for the heater - and well positioned for a short exhaust...

 

In terms of ducting, I presumed it would simply be feeding one through to the inside of the boat to a single outlet for the hot air - but the mechanic has advised hot air ducts down the length of the boat with additional outlets. I feel like it's good advise for optimum heating, but not wholly necessary? What's your set up? 

 

On 06/05/2026 at 11:32, Tony Brooks said:

Look at the dates of posting, things seem to have improved considerably since low sulphur diesel was mandated.

 

That suggests that you, or he, are thinking of fitting a hot air Webasto which tended to be more reliable than the hot water ones Mrsmelly was talking about.

 

All our hot air Webastos on the Thames hire fleet were ducted to ensure hot air was supplied to every part of the boat not much above floor level.

 

and how do you suppose a blast of hot air from the back of the boat up the corridor will turn through 90 degrees to get into the bathroom, by the time it got there the hot air is likely to be running along the roof.

 

Thanks Tony, yes a hot air Webasto.

 

Good to know some of the issues in the past were caused by the type of diesel, thanks.

 

Yes, ducting along the boat as you have done is what has been recommended to me. However, I presume (like my stove) the heat will travel down the boat... Not as effectively, but a good improvement on my current set up. Of course the heat will rise (as it does with the stove) - but surely there will be some benefit to a single outlet? 

On 06/05/2026 at 11:43, cuthound said:

 

When I bought my boat it was 7 years old and the Webasto had been serviced every year (I got a file with all receipts in it when I got the boat).

 

My surveyor told me what you suggest. Run it hard for an hour then turn it off to let it cool down. This burns off the carbon deposits and negates the need for annual servicing.Don't run it on part load and don't get it serviced until it obviously needs it.

 

The boat is now 19 years old and the Webasto works perfectly. It hasn't been serviced for 12 years now.

 

Thanks cuthound. So basically run it on full blast, in shorter bursts? An hour on full to heat things up, rather than lower for longer? 

13 hours ago, matty40s said:

Not entirely....

There have been a lot more problems with fuel pumps on systems that are not used regularly....not a difficult job to fix with an external Webasto fuel pump, but slightly more involved with the internal eberspacher pump.

Thanks Matty, good to know.

[Tony Brooks]

51 minutes ago, Hunter1 said:

Thanks cuthound. So basically run it on full blast, in shorter bursts? An hour on full to heat things up, rather than lower for longer? 

 

I suspect that if installed as you propose the blower noise will encourage that sort of use.

[Alan de Enfield]

18 hours ago, Tony Brooks said:

 

I suspect that if installed as you propose the blower noise will encourage that sort of use.

 

we have a  'blown air' system, (8kw Eber) and it can hardly be heard inside the boat, but, outside it can be heard for 'miles' as the sound (like a rocket engine) travels across the water.

[blackrose]

On 06/05/2026 at 11:43, cuthound said:

Don't run it on part load 

 

 

So take any thermostatic radiator valves off. They should just unscrew.

 

*Sorry just realised the OP is talking about a hot air Webasto. There must be a reason hot water Webastos are more popular on narrow boats? Probably to avoid all that ducting and vents the OP talks about. But is installing a CH system any easier?

Edited May 8 by blackrose

[Tony Brooks]

26 minutes ago, Alan de Enfield said:

 

we have a  'blown air' system, (8kw Eber) and it can hardly be heard inside the boat, but, outside it can be heard for 'miles' as the sound (like a rocket engine) travels across the water.

 

Yes, but I bet yours is properly ducted and not just a single vent into the back cabin and hope it warms the rest of the boat. I also suspect the pipe to each outlet leaves a main trunk via a right angle and think that will tend to absorb some blower noise.

[blackrose]

On 06/05/2026 at 10:50, Hunter1 said:

.Note: I'm not intending to use it as a replacement for my stove (which is at the very front of the boat) 

 

 

A design error that's seen on probably half the narrow boats on the waterways.

 

Stoves at the very front of the cabin are installed in that position purely for space saving reasons. It might be ok on a <50ft boat, but for anything longer it's a mistake.

[phantom_iv]

53 minutes ago, blackrose said:

There must be a reason hot water Webastos are more popular on narrow boats?

Apparently some boaters do appreciate the occasional hot shower?

[blackrose]

21 hours ago, Hunter1 said:

Thanks cuthound. So basically run it on full blast, in shorter bursts? An hour on full to heat things up, rather than lower for longer? 

 

 

The basic regime is to run them for an hour or longer, just not less than an hour. 

 

In order to get the water heaters to keep running on full blast after the whole CH system is hot, it's recommended that the amount of rads, pipework, etc, add up to the boiler output. In many cases the CH systems on boats aren't sufficiently sized meaning water returns to the boiler still hot because the CH system hasn't been able to get rid of the heat. Then the boiler starts to cycle down and potentially coke itself up, although this situation was obviously worse with the old red diesel. 

 

With your hot air blown heater that obviously doesn't apply, but the point is make sure it runs at full blast, so you don't want any thermostats in the cabin picking up air temperature to control the heater for example.

 

If it gets too hot just open a couple of windows and turn the heater off after an hour.

 

The other thing worth mentioning is that when you switch them off these heaters run a cool down cycle for a minute or two. Always let them run that cool down cycle and never switch them off by pulling a fuse or isolating the batteries.

Edited May 8 by blackrose

[ditchcrawler]

20 minutes ago, phantom_iv said:

Apparently some boaters do appreciate the occasional hot shower?

I haven't got one but we have a hot shower every day

[blackrose]

22 minutes ago, phantom_iv said:

Apparently some boaters do appreciate the occasional hot shower?

 

Yeah I forgot about that! 😂

[Alan de Enfield]

1 hour ago, Tony Brooks said:

 

Yes, but I bet yours is properly ducted and not just a single vent into the back cabin and hope it warms the rest of the boat. I also suspect the pipe to each outlet leaves a main trunk via a right angle and think that will tend to absorb some blower noise.

 

Yes it is ducted throughout the boat - 2 outlets in the rear cabin, 1 outlet in the en-suite, 1 outlet in the saloon, 1 outlet in the dining area / galley, 1 outlet in the forward head, and one outlet in the forward cabin.

 

Thermostatic control in the saloon,

[Gybe Ho]

2 hours ago, Alan de Enfield said:

 

we have a  'blown air' system, (8kw Eber) and it can hardly be heard inside the boat, but, outside it can be heard for 'miles' as the sound (like a rocket engine) travels across the water.

 

I noticed the same walking around countless coastal marinas. I eventually concluded Webastos transmit more noise into the cabin than out of the exhaust whereas Ebers have the reverse noise profile. If true I deduce your ducted hot air system has a Eberspacer?

 

OP: It is possible to fit a noise muffler to the internal ducting of a Webasto.

 

On 06/05/2026 at 10:50, Hunter1 said:

Slightly concerned after searching "Webasto" on here that there were approx. a billion posts about issues with them! 

 

 

This is unrelated to the Webasto brand which is arguably the Mercedes of forced combustion diesel heaters in the boating world. All these devices are temperamental delicate mechanical dandy's that will throw a tantrum unless installed perfectly and operated with an ideal usage pattern.

 

You say you cannot afford a wet radiator installation but I know how you could. Become an authorized service engineer for Webasto and Eberspacer heaters

Edited May 8 by Gybe Ho

[Alan de Enfield]

2 hours ago, Alan de Enfield said:

 

we have a  'blown air' system, (8kw Eber) and it can hardly be heard inside the boat, but, outside it can be heard for 'miles' as the sound (like a rocket engine) travels across the water.

 

 

12 minutes ago, Gybe Ho said:

I deduce your ducted hot air system has a Eberspacer?

 

2 hours ago, Alan de Enfield said:

 

we have a  'blown air' system, (8kw Eber) and it can hardly be heard inside the boat, but, outside it can be heard for 'miles' as the sound (like a rocket engine) travels across the water.

 

 

12 minutes ago, Gybe Ho said:

I deduce your ducted hot air system has a Eberspacer?

 

[cuthound]

1 hour ago, blackrose said:

 

The basic regime is to run them for an hour or longer, just not less than an hour. 

 

In order to get the water heaters to keep running on full blast after the whole CH system is hot, it's recommended that the amount of rads, pipework, etc, add up to the boiler output. In many cases the CH systems on boats aren't sufficiently sized meaning water returns to the boiler still hot because the CH system hasn't been able to get rid of the heat. Then the boiler starts to cycle down and potentially coke itself up, although this situation was obviously worse with the old red diesel. 

 

With your hot air blown heater that obviously doesn't apply, but the point is make sure it runs at full blast, so you don't want any thermostats in the cabin picking up air temperature to control the heater for example.

 

If it gets too hot just open a couple of windows and turn the heater off after an hour.

 

The other thing worth mentioning is that when you switch them off these heaters run a cool down cycle for a minute or two. Always let them run that cool down cycle and never switch them off by pulling a fuse or isolating the batteries.

 

No, you want to run it and stop it before it drops to half power.

 

These heaters create carbon from incomplete combustion when not running at full load. Leaving them to drop to half load for long periods is a recipe for increased servicing.

[LadyG]

I have a stove in the saloon, with back boiler, to small rad in the bathroom. The webasto has two large rads which are usefull but not essentisl. I run my stove 24/7  in winter, with the Webasto run on the thermostat.

It is excellent as back up. I had it serviced when it started exploding. It should be serviced before that! Mine was leaking fuel!

I should be run every month to burn off crud. Min. burn time 1 hour. My whole system needed flushed, it was 26 y.o.

Reliable, unless you are very short of cash and competant,  buy the industry standard,  sometimes re furbed are on Ebay.

Edited May 8 by LadyG