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high or low revs for hot water


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Hi all, I have a nanni raw water cooled engine that also heats the hot water.

Will the water heat up quicker with high or low revs, this is obviously when on the mooring and not at Un sociable times. 

Any thoughts



We have a Nanni too, Mark.

I wouldn't dream of heating the water by running the engine at whatever revs, because you're not putting a load on it and the consequent glazing of the bores will eventually cause you problems.

Yes, I know the hire boats do this but they also spend a lot of hours at high revs which probably offsets this.

I found that our calorifier had connections for 230V on it and I wired this in to the 230V system.

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I was told by a well known boatyard to leave the boat ticking over in gear, thus creating a load (not ideal if other boats are close by). That said, we had a narrowboat for 20 odd years and that was run out of gear many, many, many times and there were no issues. We also have a fitted 240 volt immersion heater but unfortunately there are no sockets in the middle of Barton Broad  :smile:  

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I used to run the engine at a fast idle (I.e. Just a little over tickover) when I had my first boat in order to heat the water. A cold engine will warm up faster than at tickover that way. Best of all is under load of course. Sent from my iPad using Tapatalk HD

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This is not for everyone but I deal with things for hot water requirements.


I get up and put on the kettle.  Once boiled I add some cold water in the sink first (don't think wise to pour boiling water into a plastic sink) and then I can wash and shave, brush teeth and get ready.


Leave mooring.


Moor up at my destination and the water is now piping hot and one could have a shower.  Of course if there is a couple of you on the boat, as you are going along one can steer the other can shower and the hot water is being replenished by the engine.


I have to confess I'm not in the camp of thinking one needs an immersion heater on a boat, since in the main they would require the engine to be run to provide enough power to operate (thus cancelling out the electric element).


Other option is find a mooring with 204v power hook up, which is great but then in all my times afloat I have only been at two moorings where there was an actual free electric point within 'range' of the boat. Since preferring out of the way moorings, which do not tend to be ones where electric points are provided if I was to have a boat and such had an immersion heater the electric side of the operation would hardly ever be used.

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Robin it talking like someone who hires boats. A lot of private owners who live not too far from their boats like to pop down to the boat and relax onboard at the moorings, If they have a hook up then a immersion is Ideal, pop it on and have the luxury of hot water. when you own the boat and can use it when you like, you do not need to hit the river for every minute possible to get the most cruising for your money.


If the boat in question is the one in the pic then I do believe I know where your moored and is im not mistaken you have a livaboard just a few boats down also being on a tidal river but not a floating pontoon your ropes will not be that tight as there is a 4' rise and fall on the river. and running engine in gear might get you a bit up close and personal with the boat in front (or rear), I should stick with firing up and running on tick over or just over tick over if tick over puts a lot of vibration through the boat, you could put some revs on for 5mins to bring the engine temp but once up to temp there is no point in continuing at a faster RPM.  

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have a cold shower, it looseen the bowls .................!!!!!


and invigorates the mind make a good start to the day ......................



aquavista .......................the fountaine of youth ................drink a bit orf river water now and then .....!!!!



or run it a different revs and see which works best for yer set up, easy ......


make sure yer tank is superb insulated or put extra round it top and bottom cover it complete keep that ole heat in .......


check that ole pressure releif valve too yer can loose alot or water if stuck on drip mode ....!!!!!



and the advise above all goods yer know from others too

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