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Old 03-05-2017, 10:17 AM   #1
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Diesel engine warm-up?

Back in the day, especially when engines were carbureted, many people used to warm up their cars before driving off. Nowadays the general guidance by experts is that you should pretty much just drive off but stay at a reasonable rpm until the engine fully warms up.

What is best practice for a boat? I have modern diesels (twin Volvo D4-300). So far, I've been letting the engines come up to operating temperatures before heading out.

Or should I be following the same guidance as with cars and just fire up the engines, wait just a little bit for oil to fully flow, and slowly head out?

Thanks!
Mike
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Old 03-05-2017, 10:32 AM   #2
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Tony Athens has written some pretty compelling arguments as to why allowing our diesels to idle at the dock is a bad idea. I certainly don't understand it all but a lot has to do with how long it takes the engines to get up to true operating temp while not under load. I think the concern is more about oil temps than coolant temps. His suggestion is to be ready all ready to depart before the engine is fired up. As soon as you verify that the engine is running normally (oil pressure is up, water is flowing through the cooling system, etc...) then leave.

You may want to wait to bring the power up a lot until the engine has warmed up, but in my case I have a good 15-20 minutes before I leave my no-wake harbor anyway.

I only know what I read, but tend to trust what Tony Athens writes.
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Old 03-05-2017, 10:35 AM   #3
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That's what I do. Start and go. Makes for a much better neighbor as well.

Aftercooled engines in cold water may never warm anyway.
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Old 03-05-2017, 10:38 AM   #4
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Waiting for a diesel engine to warm up while not under load is like watching grass grow. Fire it up and leave. Keep the rpm low until at operating temperature. I start out at about 1,000 rpm and gradually inch the rpms up as the engine warms to operating temp.
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Old 03-05-2017, 10:39 AM   #5
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Our Great Harbour has twin Yanmar 4JH3-TEs and the manual recommends:
4.3.4 After the Engine has Started
(1) Warming-up running
After the engine has started, let it run for about 5 minutes. This warms up the engine and distributes oil to all of the parts.
NOTICE:
The engine will seize if it is operated when cooling seawater discharge is too small or if load is applied without any warming up operation.
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Old 03-05-2017, 10:46 AM   #6
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Our Great Harbour has twin Yanmar 4JH3-TEs and the manual recommends:
4.3.4 After the Engine has Started
(1) Warming-up running
After the engine has started, let it run for about 5 minutes. This warms up the engine and distributes oil to all of the parts.
NOTICE:
The engine will seize if it is operated when cooling seawater discharge is too small or if load is applied without any warming up operation.
Now that's scary.
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Old 03-05-2017, 10:47 AM   #7
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Indeed!
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Old 03-05-2017, 10:53 AM   #8
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Quote:
Originally Posted by bayview View Post
Aftercooled engines in cold water may never warm anyway.
No problem warming up my coolant cooled after cooled engines quickly in 45 degree water.
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Old 03-05-2017, 11:00 AM   #9
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Quote:
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No problem warming up my coolant cooled after cooled engines quickly in 45 degree water.
Same here, my closed system with thermostat could care less what the water temp is. The thermostat won't open until it gets to rated temperature. Now starting my Detroit's when ambient temperature drops below 60 can be a challenge, but once started doesn't care.
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Old 03-05-2017, 11:06 AM   #10
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The manual for my JD 4045 specifically warns against idling for more than a few minutes. On start up, I usually let it fast idle for about a minute while I throw off the last 2 dock lines and then go. The area that is much more of a concern for me is waiting to lock through. Some of the waiting areas in front of locks can require frequent bumping in and out of gear while you wait for 20+ minutes. Pulling an anchor in the morning can involve a significant amount of idling time also.

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Old 03-05-2017, 11:19 AM   #11
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From our dock, start,, pull in the lines and GO

Moderate load 1000 -1200 RPM is good to have enough load that the engine will warm up and return to operating shape and temperature.

Save higher loads and RPM till at least 140F , and wait for full coolant temp before WOT.

At anchor we just keep a single turn on the windlass till straight up and down , then 2 quick turns and it pulls the anchor up to the roller.

We use a small 12# Danforth for bridges we cant slide under while we wait for passage.No Ideling.
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Old 03-05-2017, 11:22 AM   #12
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In 1973 I built a boat and installed a Cummins V-504M engine.

The book said to start the engine and run at high idle, 800 - 1000 rpm, for
5 minutes before applying load. At shut down take the load off and run at high idle
for 5 minutes to cool down before turning off.

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Old 03-05-2017, 12:02 PM   #13
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You want engine fully warmed up before adding a heavy load, but a light load like a trawler engine at hull speed, no problem. Just crank it, throw off the lines and go.

On my planing hull boat, If I plane out before thermostat opens, temp spikes pretty high then drops, then rises to normal. Seems like a thermal shock so I avoid it. Now I cruise at low speed til temp stabilizes, takes about two miles.
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Old 03-05-2017, 12:23 PM   #14
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High performance engines, and some NA engines with sea water cooled oil may never get to operating temps at idle. That oil cooler is sized to remove all of the heat in the oil at wot, but at idle the engine is putting out very little heat but raw water is still gushing through that oil cooler and it can often take the full heat output of the engine, ie no heat is required to be removed with the coolant/raw water exchanger so the thermostat never opens.

So let me add my voice to the developing consensus: start your engine, throw off the dock lines and idle out of the slip, increasing the throttle when conditions allow to 1,200-1,500 rpm to let it warm up to operating temps before putting any significant load on the engine.

And unless you somehow do a quick shutdown immediately from high load, you almost always have time to let the heat load stabilize as you make your way to your dock or anchorage. Even if you do pull the throttle back instantly, I don't think that most marine diesels with jacketed turbos will be damaged by heat soak like car turbos can be.

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Old 03-05-2017, 12:46 PM   #15
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If you measured and plotted out oil temp, EGT, and cooling circuit temps, you'd get some pretty disparate curves until you reach a steady state equilibrium. So warm up is a figurative term at best.

Ski will remember we used to warm up the old 38ND8 1/8 until oil temp was 90F, ramp up the electrical load on the generator and then ready for a full load at 160F. Tugs with the same engine would push on the pier or wharf to load it up.

That's what the engineers determined for that particular engine.

On my teeny tiny Volvo, I start it up, watch oil pressure come up, check water flow out the exhaust, test my thruster, and cast off lines. Idle out the fairways, and slowly increase load once I clear the breakwater as I watch coolant temperature come up to normal. Occasionally check exhaust for water and color of exhaust.

Coming in, I use a prudent speed approaching an entrance or anchorage. Usually maneuvering in the marina or around the anchorage gives me adequate cool down time. Shut down when lines or anchor is secure.
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Old 03-05-2017, 12:56 PM   #16
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We do the same as other - start the engine, check to be sure all looks good, then get cast off and underway. Just no heavy loads until it's at operating temp.

In practice, by the time we get off the dock and into clear water, the engine is at or near operating temp anyway. If not, I just keep it at a modest load until it is. Very rarely am I waiting for the engine to get warm. It's usually ready by the time I am.

Similarly when coming in to dock or anchor. By the time you putter up to the dock, maneuver into place, get tied off, and are ready to shut down, the engine has had plenty of time to "cool down".
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Old 03-05-2017, 01:10 PM   #17
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What's just as critical for a diesel is to let it cool down gently after a hard run at high temps to allow it to cool evenly avoiding 'hotspots' and relieving thermal stresses.
Volvo's subjected to lots of idling will also be prone to develop oil leaks.
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Old 03-05-2017, 01:10 PM   #18
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How many different discussions are here where not giving a rats rear end will accomplish 99% of what you want and 1% of worrying about what NASA will worry about is the last little bit.


Warm up is only as important as the load you will demand as the time comes....think slowly and it will come to you....
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Old 03-05-2017, 01:51 PM   #19
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The emphasis here on this thread seems to be what to do at the dock/float.

What's more important IMO is what to do after one leaves the moorage. I leave at 1400rpm (3000rpm engine) but it takes 10 or 15 minutes to get to cruising rpm. Increase about 2-300rpm every several minutes w longer pauses while getting toward the cruise rpm. Could take 20 minutes. Actually I'm sure much of the time I do take 20min.

And as IR writes cool down slow. Again IMO not about long idling at the float but slowing down quite far out while approaching the destination.
The cooling down is much more important for turbocharged engines.

Personally I don't idle at the float longer than it takes to take care of the lines and tend to deck issues. Unlike many here I do'nt strive to have as low an idle rpm as possible. One of the advantages is that I can back out of a slip and pause in neutral before going into reverse gear w/o any chance of the engine quitting. Years ago I adjusted the idle speed a tad (100rpm ?) or so high and have'nt changed it since. The only reason one would want to have a low idle is if they were overpropped. But even then I do'nt think putting the trans in and out of gear often is troublesome at that speed and load or makes excessive wear. As long as the shift is done quickly.
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Old 03-05-2017, 04:40 PM   #20
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The so called warm up is covered above. What is also in my manual is notations not to put the engine under sudden load or high rpm when first started. Here is where a minute or two at no load idle allows for oil to circulate and in gear at idle would do the same. On a practical basis the time it takes to cast of usually takes care of any oil circulation issues. This whole issue is probably more important with gen sets where a higher rpm is pre determined. There it is best to start and run without load for a while then add load gradually. Cooling down has already been posted and can be as important as start up.
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