Running engine at anchor for hot water - load

[Letterkenny]

I have read some threads here on this and know of the general note that running a diesel not under load is bad for it. I have a Yanmar 3YM20 and am looking to do some longer trips on it. It seems much more efficient to run the main for heating water and also helping add power to the house bank than using the water heater connected to a Honda generator. My concern is the lack of load (this will be pushing the button on the throttle to enable a higher RPM while still in neutral gear). What are the main concerns or considerations to have here? Is it potentially putting it in reverse at anchor or on a mooring ball to add load while the engine heats up/charges the batteries?

[clownfishsydney]

Had 3YM30s in my cat. No problem, just don't do it for heaps of hours.

[HeinSdL]

Putting it in reverse also heats the water much quicker. Just mustn't swim near the boat at the same time.

[Muaddib1116]

Originally Posted by Letterkenny

I have read some threads here on this and know of the general note that running a diesel not under load is bad for it. I have a Yanmar 3YM20 and am looking to do some longer trips on it. It seems much more efficient to run the main for heating water and also helping add power to the house bank than using the water heater connected to a Honda generator. My concern is the lack of load (this will be pushing the button on the throttle to enable a higher RPM while still in neutral gear). What are the main concerns or considerations to have here? Is it potentially putting it in reverse at anchor or on a mooring ball to add load while the engine heats up/charges the batteries?

Much more efficient in what way? How much power does your water heater element use? I assume you plug your shore power into the Honda? Why not heat water and charge the batteries off that? Even if it's less efficient in some way, I'd much rather put hours on a cheap generator than put low load hours on my engine.

[Scubaseas]

Second putting in reverse. Mind you might start doing circles due to prop walk. If in gear you have a load on the engine and it will heat the water faster. Run motor at WOT in neutral for 20-30 seconds before shutting down to help clear the exhaust. Your manual may or not mention this but later Yanmar manuals do.

[Calif.Ted]

Because it takes engine so long to warm up while not under load it seemed more efficient to run a Honda to me. tied to a mooring at Catalina or a transient dock anywhere else the Harbor patrol may not be receptive to your boat running in gear to heat water. Be a real potential for some problems with the fore and aft mooring lines if running in gear.

[Stu Jackson]

Ted's right. I would run my engine at 1500 rpm for a half an hour or so after two days or two nights on the hook (depending on when I arrived) to stuff 30-50 ah back into my house bank with my 100A alternator and MC-612 regulator. 100-130 ah 24 hour load at anchor, would arrive pretty full house bank, lots of motoring up here. The water would only get lukewarm, not enough for showers maybe for dishes. If you have a genset, use it. I have a 21hp M25, Seaward 6 gallon 1500W water heater, no genset. Even at cruising speed 2500 rpm it'd take 45 minutes to get real hot hot water. I'd run at 1500 in neutral to get enough out of the alternator.

[CaptTom]

Yeah, it'll take forever to heat up a decent amount of hot water from an idling diesel. I'm not real keen on the idea of leaving it in gear, for more reasons than I care to list here.

The solution is a generator. Run it for an hour or so to heat up water and top off the house bank if you haven't been motoring in a while. I can generally get away with about an hour a day. You can probably hear the generator unload when the electric water heating element switches off, or watch the ammeter gauge. Besides being kinder to your main, it'll be more efficient, turning less mass at a higher load. I know some hate them, but it's hard to beat a Honda EU 2000 for this, if you have no other need for a bigger generator.

[Don C L]

I’ve probably been on a little boat too long but using combustible fuel to generate electricity to heat water for a shower seems a bit Rube Goldberg to me. Given the set-up, the generator makes sense. But a solar heater or even a kettle on the stove makes more even sense, but that’s just me.

[TrentePieds]

Ah yes -)! Never go the simple way (read "five bob kettle on the hob") when you can go the "technological" way (read $30K Diesel Engine) to do the same pedestrian job :-0!

Even in a "huge" 34 footer, there really isn't room to have a shower below decks. doing so just gets water everywhere, which takes hours and hours to clean up adequately.

What happened to the venerable "Liverpool wash"? I believe Americans call it a "sponge bath". Just so much more efficacious and agreeable aboard a yacht :-).

TrentePieds

[CaptTom]

Running hot water is a luxury I truly appreciate, ever since the first boat I owned which had it (a 28-footer, BTW.) I've been aboard many 32-34 footers with a decent shower and generator. Of course the best of both worlds is hot water from the main when motoring, and a generator for all the little luxuries which make life on the hook enjoyable. A well-sized solar system is also a viable alternative.

Sure, I can survive without them. But is survival really the goal?

[Pete7]

Originally Posted by CaptTom

Yeah, it'll take forever to heat up a decent amount of hot water from an idling diesel. I'm not real keen on the idea of leaving it in gear, for more reasons than I care to list here.

In addition to the time it takes a diesel engine to come up to temperature, at idle, a diesel engine isn't subject to the same internal pressures compared to motoring a yacht so under heavy load. Without that pressure the piston rings won't move outwards and seal against the cylinder wall allowing oil and hot gasses past. Notice that compression rings are not square in profile but one surface is tapered to encourage them to move out under pressure. The oil scraper ring also doesn't work quite as well leaving oil on the cylinder wall that then glazes with the heat of the exhaust gasses getting past the rings.

Regular use at no/slight loads means reduced compression and poor starting due to the glazing. Two ways of removing this varnish like surface, strip down and hone the cylinder walls. Option two if it isn't too bad, an Italian tune up.

We did an Italian tune up the first long trip out after purchase. 14 hours powering into the teeth of a gale which was threatening to get worse. Engine started instantly for the rest of the year.

How much is a Honda in the US? $1000 perhaps and it will last for a decade. I would use the Honda. Under load heating water and charging the batteries it will run at a good load maximising the power generated for the fuel used.

Pete

[Letterkenny]

I already have an EU2200i so I guess I’ll use that. Perhaps I’ll look at getting the new EU3200i as my main concern is trying to run it less in the day between the two different banks that I have to run and don’t always want a generator running.

[SomeGuyInaShirt]

I'm reasonably certain that during the lengthier run time between the engine starting and reaching operating temperature will lead to premature piston ring wear. Also, the diesel being injected will get past the rings and wash the lubricating oil from the cylinder walls while simultaneously diminishing the lubricity of the oil in the crank case. I'm not super familiar with marine diesels but road going diesels experience these problems when idled regularly.

Supposedly short cycling the engine will cause condensed water in the cylinder to also leak past the rings into the sump but I'm not sure how true that is or how quickly condensation in the combustion chambers is removed.

There's a reason diesel experts advocate avoiding using a diesel for low load purposes.

I agree with the people advocating simpler solutions like heating water on the stove. You can rig a rudimentary shower heater up in your regular shower stall in a multitude of ways. Think about them. Look it up on YouTube, see what works for you.

[Stu Jackson]

Originally Posted by TrentePieds

Even in a "huge" 34 footer, there really isn't room to have a shower below decks. doing so just gets water everywhere, which takes hours and hours to clean up adequately.

I beg to differ. But that's probably because my boat (1986) was one of the first "production" boats with a rather generous aft head with a space large enough for a decent shower, albeit not a separate shower "space." However, my C34's successor yacht, the C355, with pretty much the same layout down below, does have a separated shower space. I don't spend more than 30 second cleaning up. I prefer to shower on my boat rather than using shore facilities, too. Yeah, she's a huge 34 footer.
I would agree for other boats, for example the C36, built even earlier by Catalina but with a very narrow forward head.