Engine warm up time??

We had a Cummins captain run through our engine room with us and he said that diesel engines in particular like to operate on a load - any load and that warming them up is not necessary and in fact can be detrimental to the engines in the long run. He did give us a checklist of what to look for prior to starting the engines and what to look for after they've been started but he said that excessive warming up is no longer necessary.

For us it doesn't matter much since we have to get through the ship canal before hitting the salt and we would have about an hour of traveling at idle speed before hitting the lake where you can operate at a speed higher than 7 knots.

Sandy
 
Good discussion. I think whether it is a gasser or diesel I would do pre-start checks. Once engines are running, I remove verify gauges are working correctly and pressure items are in the green. Then check tyranny fluid level, disconnect lines and push off. In the winter months I run at hull speed until gauges come up past 100 degrees and then feel comfortable pushing throttle up. Long no-load is not good for any engine, but a couple minutes for system checks and cross checks does allow everything to stabilize before pushing away from the dock.


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I think we are overthinking or getting far a field from the real warm up issue. Modern EFI engines don't need a warm-up like old style carburated engines. Automakers suggested that fuel-injected engines don't need to sit in the garage and warm up. It was suggested to drive easy the first mile or so to get everything else up to temperature.

Carburated engines have chokes. That butterfly plate at the top of the carb is fully open when cold to let more air in to mix with the gas before the mixture gets to the combustion chamber. A carburated engine will die if not warmed up and the choke closes.

Cold weather, as in winter in the upper Midwest, is another story which most boats are not subject to because they are not in the water. EFI cars, however, can be driven in the winter without warm up as noted above, but at -10 with no warm up and flooring it you may experience a bent push rod or two.

I realize marinized engines work much heavier loads than an auto engine. This was meant to get back to basics with gas engines.
 
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330A has the right theory but backwards. the carb'd engine has the choke closed until it warms up then fully opens. mine will stall out if i don't let it warm up a little first so i try to see about 140* before leaving. usually takes about 5 minutes or so but i probably don't even need 140.

i have never heard of bending a pushrod because of a cold engine? a bent pushrod is a mechanical failure (which i have done a few times in my race cars:huh:). a cold engine will have more piston slap than a warmed engine due to thermal expansion but with todays piston materials that has been minimalized. forged pistons were worse than cast
 
Our SRV is carbureted. After we launch and are tied up, my wife puts the drive down and gets the engine started while I park the truck/trailer. When I get on board, the temp is starting to come up and we check the final items before shoving off. We idle thru the no wake zone in and coming out of the marina. At the point, the temp is where it should be and we're off for the days adventures. If we were fuel injected, the pre warmup may not be necessary- even with a properly adjusted choke, the engine is a bit fussy when its cold and will spit and cough until it has some temp on the gauge on throttle past idle or low throttle-1/4 or less
 
330DA said:
Carburated engines have chokes. That butterfly plate at the top of the carb is fully open when cold to let more air in to mix with the gas before the mixture gets to the combustion chamber. A carburated engine will die if not warmed up and the choke closes.
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I think you mean't to say closed and less air when cold :)

Jeff
 
My routine is to run the bilge blower for 5 minutes then start the genny. Warm up the genny about 5 minutes then switch the shore power over to the genny. Start both engines. I don't have a set warm up time but it's at least 5 minutes before we get untied and start out. Then we have at least 5 minutes at no-wake speed. So my engines are running a minimum of ten minutes at idle speed before any serious load is applied. 6 months out of the year we are sitting in 80-90 degree water so it doesn't take long to get to operating temperature.
 
Boatman37 and dieseljeff - thanks for the correction. I have to stop thinking and typing after it's bedtime.
 
This is primarily for the diesel owners who posted, but some of it may be applicable to gas engines as well:


The whole thing about warming up diesel engines is avoiding hot spots in the engines. Diesel fuel burns hot and is under tremendous pressure when it ignites .......electronic diesels can have compression ratios above 22:1, compared to your average Mercruiser, Tahoe or Lexus at about 8:1.

If you apply power too soon or before the engine reaches operating temperature, parts of the engine are cold and those parts "near the fire", i.e. the combustion chamber and cylinder liner are quite hot. Cold parts shrink,; hot ones expand, so the risk of too much power too quick means the parts away from the combustion process do not get warm before the components nearest the combustion chamber. The risk is cracked heads, cracked blocks, blown head gaskets and premature cylinder wear.

I would let the engines idle at the dock until you see the temp gauge hand begin to move, then hold the power setting between idle and about 900 rpm until you reach an indicated temperature of 160-180˚ Once you get there, its ok to apply enough power to get up on plane. This isn't an inconvenience for most of us because we usually have a no-wake or high traffic area to transit to get to open water in which to allow the engines to warm up at their own pace.

The other side of the warm up process, the cool down, is equally as important. On turbocharged engines always allow the engines to cool down after a run under power. This is for 2 reasons......1.) it allows the cooling system to dissipate the heat from being fully loaded which eliminates the hot spots I mentioned previously, and 2.) the actual speed at which a turbo charger rotates is scary fast.....like 8000-10,000 rpm. They are lubricated with engine oil and develop a lot of heat. Allowing some cool down just lets the turbo get back to ambient temperatures and slow down and avoids premature failure of a $4000 part. Follow your engine makers recommendation on cool down which is usually something like 3-5 minutes at idle before shut down. This is rarely an issue for sensible pleasure boat operators since most of us have a long period of no-wake or high traffic area to transit when returning to our slips.

In my case, I'm about 2 miles from the Gulf and have to transit and area full of tourist and commercial boat traffic and no wake zones. I run about 20 minutes at ldle every day both leaving and coming home. By the time I get to where it is safe to get up to cruise speeds, my engine are at operating temps and when I get to the slip, the engines are cool enough to shut down.

Hope that answers your questions............


Frank
 
Frank, thanks for the explanation of why we need the warm up and cool down periods. I knew we had to do it because it helps the engines, but didn't know exactly why.

You mentioned the 160*-180* temps before running up the rpm's. I must have super cooling systems because if I run at hull speed my boat never gets above 150*. It only goes above that if I run on plane, then it will get up to 170* after several minutes on plane.
 
Gofirstclass said:
Frank, thanks for the explanation of why we need the warm up and cool down periods. I knew we had to do it because it helps the engines, but didn't know exactly why.

You mentioned the 160*-180* temps before running up the rpm's. I must have super cooling systems because if I run at hull speed my boat never gets above 150*. It only goes above that if I run on plane, then it will get up to 170* after several minutes on plane.
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A more likely cause is that you have very low temp thermostats in the engines. Most later Caterpillar engines have 180-195˚ thermostats in them depending upon the engine model and AR# for their particular arrangement. The next time you see or can go by your local Cat dealer, I would stop by and ask them to look up the current recommended thermostat temp for the 3406 marine engines. I bet it is higher than 150˚. Higher temperatures equate to more complete combustion, higher efficiency and less soot/pollution. I'm not saying what you have is wrong or bad, just that Caterpillar does sometimes change things for their engines long after they are produced and there may have been a change in Cat's thermostat recommendation for your engines that may offer some benefit.
 
mquiet said:
Good discussion. I think whether it is a gasser or diesel I would do pre-start checks. Once engines are running, I remove verify gauges are working correctly and pressure items are in the green. Then check tyranny fluid level...
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I always add more tyranny fluid if my mother-in-law is with us. ;)

After starting my engines I let them run at a high idle for a few minutes to warm things up, but I always have at least ten minutes of 'no wake' speed before going on plane so everything is up to operating temp by the time the engines go to a high power level.
 
We have an older guy with an older boat in our yacht club and he will "warm up" his engines for 20 minutes or more sometimes. I'm never excited when we're put in the slip next to him during our cruises because I know I'll be dealing with fumes on my boat prior to his departure. I would say something but I doubt I'll change what must be a very ingrained habit. Plus he's super nice.

Sandy
 
My boat has a carb so I wait for the choke so that means I start her up take care of the dock lines by then she ready to go.If the next boat is not carbed I think I would do the same thing not as much to warm it up but just so i can listen to everything and feel it running.
 
dvx216 said:
My boat has a carb so I wait for the choke so that means I start her up take care of the dock lines by then she ready to go.If the next boat is not carbed I think I would do the same thing not as much to warm it up but just so i can listen to everything and feel it running.
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agree with this 100%.....it must be the 'mechanic want to be' inside of me....I like to listen and observe the engines and associated systems during the warm-up cycle just for piece of mind that all is OK before leaving out of the dock....I don't like to just crank the engines and pull out of the dock and take a chance nothing is wrong....issues are much easier to address when the boat is docked than out on the water...

cliff
 
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Similar routine for me

Sous said:
I usually end up at or close to operating temp before I get out of the slip. My routine is to fire up the engines, then check to see water pumping out the sides, climb down into bilge and peek around for any leaks/squeaks/pings/dings/etc., close the hatch, then disconnect all power/water/cable lines, check all gauges/smartcraft for normal readings, then brief the admiral on what I want her to do (i.e. plan for which lines first, tend this side or that, etc based on the wind and current), then get ready to head out. By then I'm usually at 150-160 and we're ready to go.
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