Are you killing your diesel engine?

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WayneH

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Jan 22, 2008
866
Tartan 37 Pensacola Shipyard, FL
I have been. While I was in Florida, I read an article in a boating magazine that discussed diesel engine loads, wet stacking and cylinder washdown. The article states that most cruising sailors are ruining their diesels because we try so hard to stretch each gallon we consume. (GUILTY as charged.) So I found a few articles that deal with diesel generators and wet stacking. A diesel generator running below design RPM is just like a marine diesel being "babied" to extend the boat's cruising range.

http://www.kraftpower.com/pdfs/KPC_IS_1 ... acking.pdf


http://www.powerscity.com/message_7.html


http://www.dieselgeneratorset.us/wetsta ... torset.htm


"Wet Stacking" happen when a diesel engine operates below the rated output level the engine starts over-fuel or "wet stack". Diesel engines are designed to operate with a load and operate more efficiently in the 70 to 80% range of rated output. When a diesel engine operates for a long period of time below 40% it begins to over fuel. This happens because the injection tips begins to carbonize and disrupt the fuel spray pattern. From http://www.dieselgeneratorset.us

Also, when engines run below the designed operational temperature, the piston rings do not expand sufficiently to adequately seal the space between the pistons and the cylinder walls. This results in unburned fuel and gases escaping into the oil pan and diluting the lubricating properties of the oil, leading to premature engine wear. From http://www.kraftpower.com

Solutions for wet stacking:


The obvious solution is to always run the generator set with an electrical load that reaches the designed operational temperature of the diesel, or approximately 75% of full load. Built-up fuel deposits and carbon can be removed by running the diesel engine at the required operational temperature for several hours if wet stacking has not yet reached the level where carbon buildup can only be removed by a major engine overhaul. From http://www.kraftpower.com My emphasis added.

So anyway, I've started running my engine harder for several hours when I run it. And we've upped our cruising speed. We used to run at 4 knots but recently we've been using 5 to 5.5 knots with some sustained 15 minute periods of 6 to 6.5 knots. And I think it's working. I have been seeing some soot coming out of the exhaust at the higher rpms. Fingers crossed that I and the previous owner haven't quite killed this engine.
 

BobM

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Jun 10, 2004
3,269
S2 9.2A Winthrop, MA
I have had this exact discussion...

...with a friend of mine. He would lug along at 2200rpm because he was worried about the reliability of his engine. His fears were based on bad experiences with a clogged exhaust elbow and bad fuel plugging his too small filter (2 microns and he needed a 10). He refused to change his ways until we were tied up to the dock. I made him listen to his engine purring happily at 2500 rpm in comparison to 2200 rpm (his max is 3000). You have to use your ears too.

By the way, I just spent an hour on a plane sitting next to a professional farm equipment mechanic. He agreed that you just don't baby a diesel.
 
Feb 26, 2004
21,959
Catalina 34 224 Maple Bay, BC, Canada
A very good reminder

I'm sure some skippers have short distances from their berth to their sailing. The answer seems to be: if you can't run your engine "for hours" [& I think the OP was more tuned to generator engines] at the very least get the engine up to operating temperature by running at cruising speed. This should take like 15 minutes. It's another good argument for NOT "letting the engine warm up at the dock," too.
 
Feb 10, 2004
3,510
Hunter 40.5 Warwick, RI
The east coast Volvo tech rep told me that the best way to run our diesel was to back off 400-500 rpm from WOT and run it at that speed. He said that it would run 24/7 at that point.

He also said that I should run at WOT for 10 minutes every time I go out. The claim was that practice would keep the engine clean and give an early indication if a condition was developing where the engine would not perform at WOT- like a fouled prop, dirty bottom, or a mechanical issue. I do a "power-burn" for the ten minutes at least every week.
 
May 24, 2004
6,799
CC 30 South Florida
I think it is widely agreed and accepted that marine diesel engines are designed to operate close to 90% of maximum RPM but eliminating a warm-up period and requring that the engine be ran at WOT on every outing does not seem in order with the original premise. If you place a load on a cold diesel engine it will vibrate and rock on the engine mounts in protest. To subject the parts to undue stress before they have had a chance to reach a consistent operating temperature I think does more harm than whatever fuel system maladies could result from a short idle period. I also don't see the beneficial difference from running an engine at WOT compared to running it at 90%. If any, at WOT some engines will start to overfuel resulting in increased soot. After running an engine it is also prudent to allow a cool down period at fast idle before shutting the engine down. This will allow the temperature in the components to gradually come down. Engines are built from different materials which expand and contract at different rates. Ensuring a warmup and cool down period will help these parts to better work with each other. I have never endorsed long idle periods and prefer a fast idle at around 1,100 RPM. Once I cast the lines from the dock it is good to know that I can throtle the engine up if I need to without having to wait or place undue strain on the engine.
 
Feb 26, 2004
21,959
Catalina 34 224 Maple Bay, BC, Canada
It's another good argument for NOT "letting the engine warm up at the dock," too.
By this I meant those who sit for a quarter of an hour or more "warming their engines" which is not necessary. We get the boat ready to go, start the engine, and by the time the dock lines are set to be cast off, the engine is ready to go. We motor slowly out of our fairway, down the channel between two marinas to the estuary (about 4 minutes) and then crank her up, since the temp by then is halfway to normal anyway.

There was a thread on ybw the other day about folks running their engines in locks and at docks, which is quite entertaining. http://www.ybw.com/forums/showthread.php?t=321182

Starting up your engine and THEN getting the boat ready is not a good practice, annoys your neighbors and wastes fuel.
 

jviss

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Feb 5, 2004
4,627
Tartan 3800 Westport, MA
The nature of diesel auxiliaries is that there are many times that you need the engine but simply can't absorb 70% to 80% of its output. On ours, the run time is probably 50% charging batteries at anchor, which is only a 1 HP load on average. Cruising, yes, we can wind it up and cruise for a couple to a few hours at higher loads if the wind's not blowing.

That said, ours is relatively fit after 28 years of this, with nothing more that oil changes, new injectors (once), and the typical troubles: coolant pump, seawater pump, etc. It doesn't smoke except a bit under higher loadings.

Maybe when it's 30 I'll have the head done, hone the cylinders and install new rings. :)

Generators that are exercised once a week or month with no load don't do well. The cylinders eventually glaze. A friend who worked at Westerbeke told me they would take these in (some of them huge, for hospitals, etc.), put a teaspoon-full of feldspar into each cylinder, and run them with a dynamometer load for a week straight. By the end of the week they were good as new, no smoke, running strong.

If only we had a 15kW generator head coupled to these Universal M25's, and a water-cooled 15kW load, we could load them up at anchor, charging batts and heating water!

While it's not ideal to use these engines lightly, it certainly isn't fatal, and it's easily fixed once it becomes a problem. I never heard of one failing because of this kind of 'abuse.'
 

jviss

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Feb 5, 2004
4,627
Tartan 3800 Westport, MA
By the way, I read the article that you partially quote from, on dieselgeneratorset.us, and I must say that it is among the worst written pieces I have read, in recent memory. It is barely English. Who are these guys? Some paragraphs don't even make sense. For example:
For small business or residential application wet stacking can be taken care with the use of an electric heater or other high load appliance to make sure the genset system is not allowed to operate for prolonged periods of time.
What are they trying to say here?

I call "FUD" on this - trying to create fear, uncertainty, and doubt, in order to sell their product or service.

Have you ever heard of an engine being 'ruined' by running it lightly loaded?
 

WayneH

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Jan 22, 2008
866
Tartan 37 Pensacola Shipyard, FL
So OK. I had trouble finding the original article when I first posted this. So here you go:

http://www.sailingmagazine.net/component/content/article/1150

But now that you think I'm FOS, I found another article in a different magazine:

http://www.sailmagazine.com/boatwor...l-mechanics-think-every-boatowner-should-know

I bought my 32 year old Westerbeke 50 back in February 2011. It was mounted in my 1980 Tartan 37 and the original warranty has run out. Although it seems to be running fine right now, I'm still trying to learn everything I can to keep from replacing it anytime soon. I have the service manual but the operating manual and the maintenance logs are missing. I had to learn Sail Magazine's #4 all on my own, though. The service manual reminds me of "The Onion" reports. Just enough real information to make the fake stuff believable.
 
May 27, 2012
1,152
Oday 222 Beaver Lake, Arkansas
A boat engine is not the same as a generator. As long as its in gear a boat engine is always under a load. While I agree full load for 10 minutes is good, it isnt critical to do so all the time. But clearly once in a while would be good for them.

These boats have engines that are way overbuilt for their application. In proper conditions most would likely surpass 20,000 hours before wearing out. They are dying young because of neglect. Lack of regular oil changes. Lack of regular checks of timing, cleaning injectors, and only putt-putting the engine in and out from dock, then abandoning it for months at a time. There are factual reports of diesels that ran continuously as pumps on oil fields for 30 or 40 years straight, never shut down, oil changed on the fly, that showed virtually zero internal wear after a teardown.

The problem with the generators is that even at no load they are always running at governed speed, either 1800 or 3600 rpm. At light load the rings arent loaded at all for that speed and the cylinders begin to glaze. Some have shown trouble in as little as 100 hours. By comparison, if its propped correctly your boat engine is always under an appropriate load for the throttle setting and always loading the rings to some extent. So while I wouldnt want to constantly idle around in gear, I wouldnt be concerned if I wernt always hitting full throttle either.

Wet stacking is a problem associated with two stroke Detroits left idling for long periods, and it refers to loading the exhaust manifold and muffler with wet unburned fuel, which smokes like crazy when power is reapplied. Four strokes dont really have that problem. The Detroits only have real trouble with it at lower temps and especially if not in good condition. Im pretty sure you wont find any Detroits in a small sailboat. They did use them in a lot of large industrial generators used for hospitals and such but you wont find many today.

Not running the engine long enough to reach full operating temp is a critical issue, and one everyone should try to correct. The engine is thermostatically controlled and should reach full temp within 20 minutes in anything above 40F, idling or not. If you let it idle at the dock 5 or 10 minutes before leaving, idle out a ways, then take it up above 1/2 throttle or more for 10 minutes or so before throttling back to idle for a minute and shutting it down, youll never wear it out in a lifetime.

If you would just take reasonable care of these engines and run them more often most of them would rust out from the outside before they would wear out.
 
May 27, 2012
1,152
Oday 222 Beaver Lake, Arkansas
I call "FUD" on this - trying to create fear, uncertainty, and doubt, in order to sell their product or service.

Have you ever heard of an engine being 'ruined' by running it lightly loaded?
Yes. But they are talking about generators, not boat engines. And wet stacking is not the correct term. Read my other post.
 
Dec 8, 2007
303
-mac 26M -26M tucson-san carlos mx
wet stacking is a BS local yokle term,not an offical technical term used in any publication by any diesel manufacturer.marine diesel,auto diesel,truck diesel are all the same, they do need to reach operating temp as does any internal combustion engine to burn off moisture and solvents which accumulate in the oil and are the most damaging to an engine,as far as rpm speed once any engine reaches peak torque(its most efficent speed for complete combustion)which on the majority of diesels is near 1500rpm there is no harm or danger in any way that will be subjected to your engine,the only correct reason mentioned on this thread sofar supporting full throttle operation was it is the best indicator of engine health,i.e fuel filters,injection pump and injectors are all in good shape if you can spin your engine at 2900rpm.where as at 1500 you could have a partially clogged filter and not be aware of it.and most all of these points apply to all engines gas 2cycle 4 cycle diesel.
 
Apr 5, 2011
113
Hunter 34 Tilghman Island, Md
When I took my diesel maintenance class at Mack Boring (well worth the money!) when the subject came up of people with short run times (most of us), the instructors suggestion was to take the boat out at least once a season and run it like a power boater would for the day. The admiral and I do this a couple of times a year when it's a nice day without wind.

I agree with most of the other posters, let the engine run for a few minuets to get the oil circulating and the engine to start to warm up. Putter on out of the marina and than run the sucker at 70-90 % of max RPM. When shutting down switch to idle for a couple of minuets and shut off.

You want long life? Change the oil and filter regularly, use clean fuel, keep the cooling system in good shape, run the engine!
 
Apr 15, 2009
76
Hunter 27 beacon ny
Yes, we(wife and I) took that class at the NYC boat show a few years ago.. He wanted that diesel throttled up under way to "boil" out the moister (water) that builds up in the lube oil. So when my wife says its time to "boil some water" its not time for tea but time to throttle up. She is also the Chef Engineer on our 79 Hunter 27.
 
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