Idle or no Idle or charge or no charge

I've been mystified on various positions regarding running our diesels to charge a battery bank while at rest, for say several hours. I can understand both sides of the argument, however, is the load of an alternator on a diesel enough to off-set what would be considered a harmful no-load condition or idle? Or does simply having enough RPMs the key.

Apparently here is what happens when a diesel engine is idled:

-Timing gear backlash [gear rattle] is maximized, leading to increased wear
-The cylinders get glazed, leading to low compression
-The engine is run at below operating temp, leading to carbon accumulation in the combustion chamber, injector tips, piston rings, piston crown, valves heads, seats, and stems, exhaust manifold, etc. Carbon on these parts will lead to accelerated wear, and possible piston ring sticking and low engine compression.
-Also, the injected fuel gets past the piston rings, because the engine is not at the correct temperature, and dilutes the lube oil. This compromised oil is sent to ALL the engine bearings, where it increases bearing wear.

With all that in mind, would it not make sense to run in reverse while charging on the hook for a load (their goes the transmission!). Does sound stupid.. or is it?

Running in reverse to put a load on the engine while charging sounds like a reasonable idea - but the reality is that it probably won't be workable unless you have a really big anchor and a great set - or a wimpy prop. And my guess is that if you did to it for any length of time the resulting set on the anchor would make it almost impossible to retrieve. On a mooring that might be different. But even so, on a mooring or lying to an anchor, if I were running a good reverse thrust I would want to essentially post an anchor watch, just to be sure we didn't start making way in reverse. That would make for a pretty stressful charging period.

Any..

Any properly set, properly sized anchor can certainly do this but with prop walk you'd be doing 360's in the anchorage while everyone else is pointing to the wind...

Solar, wind, energy conservation and LED's are your friends, diesels are $$$$$$$$$$$$$$...

P.S. Posted from the hook using a net book (8 hours battery life), lit by Sensibulbs, and my beer, Vodka & wine is kept cold by a SeaFrost holding plate. Four LED Sensibulbs running, my food at 36 degrees, the stereo, anchor light and a Bora Caframo fan and I'm still under 1.6 amps..

Engine Wear

I think that running the engine causes engine wear. I also believe (like Maine Sail) that conservation is a key element. For power replenishment I prefer the solar panel solution over mechanical means. Just my bias.

That said, a boat on an extended cruise still needs to run the engine some to recharge the batteries AND to keep the engine in good running order. Even when we're land bound and not on the boat, we try to run the engine for an hour each week. That does a couple of things for us. One, it circulates the engine oil and two it gives us an opportunity to discover problems before they get serious or give us grief when we're out cruising. It also helps keep our carbon footprint on a par with our SUV driving friends.

If your boat is on the hard for say 6 months or a year, I think you would be ahead to release the compression lever and spin the engine for 30 seconds or a minute every month or couple of weeks just to circulate the oil.

I think that the 'difference' in engine wear between running the engine under way and running the engine at anchor is greatly exaggerated.

Provided that you run the engine for 10 or 15 minutes after it reaches normal operating temperature, you will not be causing appreciable 'extra' wear over what you would have caused by the same amount of time underway. I would also engage the transmission, once in forward, once in reverse for a few seconds,occasionally, not to load the engine but just to move the tranny fluid about.

If your engine sits idle for long periods of time, oil will slowly drain from the metal surfaces and allow moisture to condense on those surfaces. That moisture will cause rust. Even small amounts of iron oxide will wear out the engine internals much more quickly than the hour or two of 'idling' time will from 'lack of load'. Over a period as short as a few months, enough rust can build up to seize rings.

Running the engine to operating temperature plus 15 minutes serves to boil off any of that small amount of moisture inside the engine while recoating everything with oil.

Loading the engine causes wear too. It's just that an engine under load will come up to operating temperature faster than one idling at no load.

Also I would add that when I'm charging batteries, I run the engine up to 1500 rpm or so. I find that's about the minimum rpm where the alternator will put out at near maximum amps. Then when we're done charging, I run the rpm up to full throttle for a few seconds. I think that this helps blow out whatever carbon build up might have occurred during the run cycle. I do this as a matter of habit whenever I shut down the engine not just after a charging cycle.

I'm just sharing my experience here but our 26 year old Universal 5432 still runs great. I'm not certain how many engine hours are on it but since we've owned the boat, we've logged about 2400 hours on the engine. The engine hour meter wasn't working when we bought her but it showed 1400 hours or so on it at that time. I'm guessing here, but if the engine life is 10,000 hours, I'd say we're about half used up. Just wishful thinking but I'll be happy to get another 26 years out of her.

Come to think of it, I'll be real happy to get another 26 years out of me.

Makes sense to me!

Thanks.. Like I said, the subject has always mystified me, since there is the real world common sense approach and then there is the master mechanic half empty view.

I do not lose sleep over idling at 1500 to charge batteries. I do not have solar or wind and do not use a slip so I have to run my motor to charge batteries. I try not to do it just for the sake of charging and hope that every few days I will need to motor somewhere at which point my batteries will get charged. I am pretty good at sailing on and off my mooring but will run the motor instead and try to get it to temp before I need to shut down.

I do use low draw LEDs(Sensibulbs) at night and only run the fridge when motoring.