How long does it take the engine to heat water?

[Blob Fish]

I realise this might be a 'how long is a piece of string' type question, but it might not, so thought it worth asking.  

 

We had been getting our hot water from using our eberspacher, but I tried showering just using water heated by running the engine for a couple of hours in neutral, and the water was.......not cold exactly, but neither was it anywhere near as hot as when it's heated by the eperspacher. It was tolerable at best, and that was just using the hot tap. 

 

Does it take a long time to have properly hot water as a 'by-product' of running the engine? Or it is our boat? 

Edited May 26, 2021 by Blob Fish

[Athy]

I suspect it's a piece of string job, perhaps dependent on the size of your engine. Two hours' running in neutral gives us plenty of hot water, but then our engine is a 2.8 litre. Is yours smaller? It may depend on other factors too but, not being a very technically-minded person, I'm not sure what they are.

This may sound a daft question, but your engine is water-cooled, isn't it?

[Tony Brooks]

Was that in neutral at tickover or neutral at the speed that gave the highest alternator output? The greater the load on the engine the more heat it produces.

 

What engine?

 

Type f cooling system - direct raw water cooled would do as you describe unless heavily modified.

 

If skin tank cooled I would initially suspect the engine thermostat is messing,  jammed open, or there is an airlock in the engine calorifier circuit.

 

 

 

 

[Alan de Enfield]

14 minutes ago, Blob Fish said:

I realise this might be a 'how long is a piece of string' type question, but it might not, so thought it worth asking.  

 

We had been getting our hot water from using our eberspacher, but I tried showering just using water heated by running the engine for a couple of hours in neutral, and the water was.......not cold exactly, but neither was it anywhere near as hot as when it's heated by the eperspacher. It was tolerable at best, and that was just using the hot tap. 

 

Does it take a long time to have properly hot water as a 'by-product' of running the engine? Or it is our boat? 

 

Running at tickover will only generate minimal heat so very little 'surplus heat' available to go into the water.

Try increasing your revs to 1500 and try that.

 

Or

Try going for a cruise at fairly high revs for a couple of hours and I bet you'll get hot water.

 

DO NOT run your engine in gear along side, not only is it illegal it damages the banks.

[Bee]

2 litre engine at fast tickover heats our small calorifier enough to do washing up, hand wash some clothes and stuff in 30 minutes but if it was a great big calorifier it would take longer. Have you got a temp. gauge? does it get to about 60 deg C or thereabouts quite quickly? If it does and the plumbing is correct then there is not much you can do about it. Low temp could mean tired thermostat or no stat at all.

[ditchcrawler]

36 minutes ago, Blob Fish said:

I realise this might be a 'how long is a piece of string' type question, but it might not, so thought it worth asking.  

 

We had been getting our hot water from using our eberspacher, but I tried showering just using water heated by running the engine for a couple of hours in neutral, and the water was.......not cold exactly, but neither was it anywhere near as hot as when it's heated by the eperspacher. It was tolerable at best, and that was just using the hot tap. 

 

Does it take a long time to have properly hot water as a 'by-product' of running the engine? Or it is our boat? 

That sounds similar to mine, The engine needs to work a bit to get hot

[Alan de Enfield]

 

Have you considered running your generator and using the immersion heater ?

 

You'll only need an hour, and it'll probably be as cheap, and won't be putting hours onto your main engine.

 

Or, why not just stick with the Eber providing hot water ? 

 

 

 

Edited May 26, 2021 by Alan de Enfield

[Machpoint005]

Our Beta 43 and cauliflower combo gives the Memsahib enough hot water for a shower after 15-20 minutes of cruising. That's provided I've remembered to open the valve in the heater circuit.

 

 

[Blob Fish]

We can't use the eber at the moment because it's broken and needs a service (probably start a thread about this too), and we won't want the heating on in summer. We don't have a generator unfortunately. 

 

I think I only had the engine in tickover - I did rev it but I can't remember where I left the stick - so it might well be that, and that does sound like a likely explanation to me, because the water wasn't cold after two hours, it just wasn't hot. 

 

We're in a marina atm so I'll try it again today and 'put my foot down' to see if that makes a difference. Thanks all. 

[Alan de Enfield]

2 hours ago, Blob Fish said:

We can't use the eber at the moment because it's broken and needs a service (probably start a thread about this too), and we won't want the heating on in summer. We don't have a generator unfortunately. 

 

I think I only had the engine in tickover - I did rev it but I can't remember where I left the stick - so it might well be that, and that does sound like a likely explanation to me, because the water wasn't cold after two hours, it just wasn't hot. 

 

We're in a marina atm so I'll try it again today and 'put my foot down' to see if that makes a difference. Thanks all. 

 

If you are in a marina the cheapest and most efficient way of heating the water is to plug the shoreline in and switch on the immersion heater.

[Tony Brooks]

17 minutes ago, Alan de Enfield said:

 

If you are in a marina the cheapest and most efficient way of heating the water is to plug the shoreline in and switch on the immersion heater.

 

Not all boats by any means have that option even if they have a shoreline socket. It needs an immersion heater in the calorifier for it to work.

[Bee]

2 hours ago, Blob Fish said:

We can't use the eber at the moment because it's broken and needs a service (probably start a thread about this too), and we won't want the heating on in summer. We don't have a generator unfortunately. 

 

I think I only had the engine in tickover - I did rev it but I can't remember where I left the stick - so it might well be that, and that does sound like a likely explanation to me, because the water wasn't cold after two hours, it just wasn't hot. 

 

We're in a marina atm so I'll try it again today and 'put my foot down' to see if that makes a difference. Thanks all. 

I usually run the engine in 'fast tickover' as it charges much better / properly and it tends to run a bit hotter however the thing that raises the temp is partly revs. per minute but also and importantly the load that the engine has. You need to find a nice big hill and give the engine some work to do or more sensibly take it  up the canal for an hour. I know running the engine in gear is very much frowned upon and in many places that really is a Bad Thing to do but  deep bits or against stone walls I would think its perfectly ok. Deep breath before I click submit.

[David Mack]

9 minutes ago, Bee said:

 I know running the engine in gear is very much frowned upon and in many places that really is a Bad Thing to do but  deep bits or against stone walls I would think its perfectly ok

 

Running in gear against decent condition steel sheet piling is probably not harmful, but doing so against stone walls is inevitably going to lead to washing out of particles from between individual stones, which will over time destabilise the wall.

There's a good reason why the practice is banned!

[Man 'o Kent]

Ball park figure, an engine produces 1/3 useful power from the energy content of the fuel it uses, another 1/3 goes straight up the exhaust and the remaining 1/3 goes into the cooling system and general radiated losses.

 

Even at tickover speeds that means there is quite a lot of energy in the cooling system so the next question is how is the cooling system organized? Is there any means of dirverting all the coolant from the engine to the calorifier until the temperatures are more or less equal or does the coolant get circulated via the calorifier and skin tank all the time?

 

 

[Blob Fish]

I tried this this morning with the engine going at about 1500 rpms, and when I tried it after 2 hours there was enough hot water to comfortably shower ?

[Tony Brooks]

1 minute ago, Man 'o Kent said:

Ball park figure, an engine produces 1/3 useful power from the energy content of the fuel it uses, another 1/3 goes straight up the exhaust and the remaining 1/3 goes into the cooling system and general radiated losses.

 

Even at tickover speeds that means there is quite a lot of energy in the cooling system so the next question is how is the cooling system organized? Is there any means of dirverting all the coolant from the engine to the calorifier until the temperatures are more or less equal or does the coolant get circulated via the calorifier and skin tank all the time?

 

 

 

On the vast majority of indirect raw water, keel and skin tank cooled engine the engine thermostat ensures virtually all the available heat goes to the calorifier until the calorifier is well on the way to reaching the engine temperature.

 

I have never seen a boat pipes as you suggest it could be but in order to get an engine heated calorifier I did run my boat with the engine, calorfier and skin tank all in series. This was with a direct raw water cooled engine modified to run dry exhaust and a skin tank. Even so we had warm water within 30 minutes and plenty of hot water after an hour but that was always with the engine running at the speed that gave the maximum charge the batteries would accept.

 

I note the OP has not answered the questions  asked back in post 3 or given any indication of having tried to check the thermostat

[ditchcrawler]

4 hours ago, Tony Brooks said:

 

Not all boats by any means have that option even if they have a shoreline socket. It needs an immersion heater in the calorifier for it to work.

I don't have one,

[Alan de Enfield]

Just now, ditchcrawler said:

I don't have one,

 

It is suprising how many folks have said "I don't have one", but when told to go and dig into the insulation, they suddenly find one, or find a previously unknown switch that all it ever seems to do is flatten the batteries.

 

(I don't include you in either category)

[Machpoint005]

28 minutes ago, Alan de Enfield said:

>>a previously unknown switch that all it ever seems to do is flatten the batteries.<<

 

 All switches do that, don't they?

(On the 12v circuit, anyway)

 

[Alan de Enfield]

13 minutes ago, Machpoint005 said:

 

 All switches do that, don't they?

(On the 12v circuit, anyway)

 

 

We have had recent examples of people cliaming their batteries go flat and all thats running is the inverter to recharge their phone.

 

Sudenly  whooooops, found a switch that said 'water heater' and it was on.

 

I have (only once) left the mooring, put the inverter on for the Freezer, cruised all day, tied up and had a full tank of very hot water, and then a few hours later the inverter low voltage alarm goes off.

 

I wonder why that happened ?

 

Now have a printed and laminated departure and arrival check list kept by the instrument panel / keys.

[jonathanA]

Equally running the inverter to charge the batteries doesn't work....

 

I've now arranged it so when running on inverter the charger and immersion heater cannot be powered off it...

[Col_T]

On 27/05/2021 at 09:57, David Mack said:

Running in gear against decent condition steel sheet piling is probably not harmful,

Probably not harmful to the piling, but what about the canal bottom?

[ditchcrawler]

3 minutes ago, Col_T said:

Probably not harmful to the piling, but what about the canal bottom?

 

3 minutes ago, Col_T said:

Probably not harmful to the piling, but what about the canal bottom?

It washes out behind it. I have seen it on quite new piling where an engine was run on a regular basis, whether it washed the bottom away first I dont know.