When charging- Engine on Forward or Neutral?

[boogie]

On an offshore trip we had to charge the battery twice a day for an hour with the alternator on the engine. The captain ran the engine with the gear on neutral.
It was on a leisure sail to Bermuda, not a race. The boat was moving nicely on a broad reach.
Is there any good reason not to charge on a forward drive?

[Klem]

If a diesel is not run hard enough, it will not get to full operating temperature and it will wet stack. If running in neutral, there is not a lot of load on the engine so you need to rev it up a bit to avoid this. Generally, if your temperature gauge is in the normal range, you are probably fine. If you look at over the road diesels, pretty much all of them have a high idle feature specifically for idling for extended periods. The exact rpm will depend on the specific engine and the ambient conditions but generally speaking, over 1500 rpm is a good start.

Running it in gear doesn't hurt and you get the added bonus of a bit of speed. The downside is that you burn more fuel even if you keep the revs low. On an offshore passage, this may be an issue. It is true that you get a little bit more cutlass bearing wear and a few things like that running in gear but they are really negligeable.

Personally, when offshore I try to coincide charging with periods of light airs and motor along slowly (1300-1500 rpm) so I put a bit of load on the engine and go a bit faster but don't burn too much fuel.

[Sea Hunt Video]

If a diesel is not run hard enough, it will not get to full operating temperature and it will wet stack.

Hello Klem:

Can you explain, in simple terms, the phrase "wet stack". Thanks

[Steve Laume]

My first question is why would you need to run the engine twice a day to charge the batteries?

Either the electrical consumption was very high, the batteries were not big enough, the charging system was not adequate or the batteries didn't really need to be charged. I have a feel there was some combination of these or other factors involved.

I keep an eye on the state of my batteries and tend to charge every couple of days when the wind is light. It makes far more sense, to me, to be able to combine charging with making better headway when the winds are light. Even if I got into a situation where the batteries were getting low and the winds were good I would still gain the advantage of having the engine in gear if I was going to have to put up with the noise anyway.

Could there have been an engine driven refrigeration compressor? Part of the problem may have been that one hour of engine time would not have been enough to fully charge the batteries, Steve.

[boogie]

to Steve
We used the autopilot all the time. We sailed with the wind on a broad reach in a confused sea, The auto pilot worked hard.
The boat did not have a battery monitor and the captain turned the engine based on his knowledge of his boat and other parameters. The boat has a 12v refrigerator connected to the battery. The captain is a liveaboard guy and sailed many miles and many years.

[CD_Sailor]

On an offshore trip we had to charge the battery twice a day for an hour with the alternator on the engine ... Is there any good reason not to charge on a forward drive?

None at all. In fact as pointed out by other writers to this thread, running the engine with a load is the recommended method. Aside, why not get to Bermuda a few hours early? In my several trips there I was always happy to see Gibbs Light sooner rather than later.

[Klem]

If a diesel is not run hard enough, it will not get to full operating temperature and it will wet stack.

Hello Klem:

Can you explain, in simple terms, the phrase "wet stack". Thanks

Wet stacking is a condition where not all of the fuel in the cylinder is burned. The cause of this is low temperatures in the cylinder causing incomplete combustion. The visible effect is that unburned fuel comes out the exhaust, it usually looks a bit more like ooze than regular fuel but you will see a nice sheen on the water regardless. The less visible effect but probably the more serious one is that your cylinder wall can become glazed making your rings seals poorly and this can develop into more of a long term problem.

This condition is pretty rare and people make a bigger deal out of it than it is in my opinion but it is definitely something that you need to keep in mind. Not running an engine up at temperature is probably the quickest way to wear one out and the second worse thing you can do is a lot of cold starts. A lot of engines that have poor compression early in their life are ones where people tried to idle them up to temperature instead of putting a small load on or idled them a lot in general. Since most of us don't have pyrometers on our engines (my trucks do but the boat doesn't) or any reasonable form of telling us what is going on, wet stacking is something that is hard to monitor for so it is generally safer to run the engine a bit harder so you are sure to prevent it. Generally speaking, if you are in gear with the engine speed several hundred over idle and your temperature gauge shows the engine to be at temperature, then you are fine.

[Sea Hunt Video]

Klem:

Thanks very much for the information Much appreciated.

On S/V Bali Ha'i, while on her mooring and when I am aboard doing maintenance work, etc. I will sometimes start the engine (1GM Yanmar 1982 model) and run in neutral at about 2,400 rpms for 45-60 minutes. I do this to keep the batteries charged and to periodically keep engine parts lubricated, etc. I do not have a temperature gauge, only a temperature light so I do not know what internal temps are at.

Since I became her caretaker in 2011 I have noticed that a small amount of almost black "powder" comes out the exhaust for 30-60 seconds or less after engine start. After that, it is clean exhaust water. Also, there is no "soot moustache" on the stern at all.

I was told by folks I trust that running the Yanmar in neutral at 2,200 - 2400 rpms was OK and would not damage or wear down the engine. I was concerned because I had previously been read somewhere that running the engine for any length of time without a load on the engine is bad.

Additional thoughts Klem

[Klem]

I suspect that you are just fine running it that way. If you see a diesel sheen on the water out the exhaust or you start to see a lot of blue smoke, I would start to worry.

Some people will run in reverse gently on their mooring or anchor if they are charging. You are trading off transmission and cutlass bearing wear for potential engine wear. I suspect that the "ideal" would be to run in reverse gently for 10 minutes or so to get the engine up to temperature and then go into a high idle in neutral but that is probably overthinking it. Best of all, if you could take it out for a spin, you would have fun and accomplish that battery charging.

[boogie]

So much good information here.

Thank you all!

Special thanks to Sea Hunt Video for taking the thread over the black hills Where No One Has Gone Before.

[pete faga]

Robert you might want to invest in a 6 or 12 volt solar charger to keep the batteries charged.You just hook up the wires to the batteries.no charge controller needed for the 6 or 12 watt.cost under one boat unit. I have mine mounted on the stern rail with Ty wraps. I believe you are on a mooring so you will get solar as wind and tide pivot Bali Hai. Pete