Does your engine warm up faster running in gear?

Most yacht engines reach the end of their potential lives prematurely because of the amount of running on tickover they are subjected to. Diesel engines last much longer when run under load.
I found that I was habitually running my engine for 30-45 minutes "warm-up" while preparing to leave the berth and upon discovering, on this forum, the harm I was doing, I resolved to warm it up at about 1800 revs in gear, (forward or reverse).
 
Actually a lot of Scandinavian specced vehicles have a diesel fired water heater underneath them. It heats the engine coolant prior to starting, taking a tremendous load off the starter motor by warming the oil and as a by-product the cab heater is also ready to go.

Rob.
 
PaulRainbow said:
Not if it's raw water cooled. More RPM = more explosions = more heat generated within the combustion chambers. This heat is dissipated into the fresh water cooling circuit and circulated by the fresh water pump. The raw water pump is indeed pump more cold water through the heat exchanger, but it isn't having any effect on the fresh water because the thermostat is closed.

Your graph shows that the temp dropped when you increased RPM to 1900, but that was after the engine had been running for 45mins and had reached operating temp. Once up to temp and the 'stat is open you'd be right to say more RPM = more cold water through the heat exchanger, by the look of it.
Click to expand...

Nope, we have a 85hp fresh water cooled diesel and it runs cooler at 1800 RPM than at 1500 RPM, but after that it's cooler again. The throughput of seawater is pretty huge at 1800!
 
If its a relatively new Beta, the same as mine, you should need to run it up to temperature anyway. Just start up and go, like in a diesel car.
 
After starting the engine I check it is charging the batteries okay and the cooling water is pumping out. By the time the mooring lines are removed and we are ready to a move off I guess three to five minutes have passed. There has been no issue with moving off on a relatively cold engine, in the summer . In the winter I might let the engine run a little longer . On the whole I try to avoid running in neutral for long periods.
It's a motorboat but I don't think that's relevant.
I doubt my engines would get up to full running temperature if run at idle. (They do get warm enough after 20 minutes for an oil change). I think running at an engine speed above idle , but in neutral, is also a bad idea .
 
One last plot, I hate running the engine at anchor -

This is yesterday running in gear at about 1200Rpm against today running out of gear at same revs.

Yesterday engine was turned off round about 07:50, today the revs were reduced to tickover at about where the 2 lines cross about 08:04

So looking at this it doesn't seem to make a huge difference running in or out of gear for the first few minutes & running at tickover in neutral will be a fraction warmer than at 1200Rpm.


Bearing in mind none of this is saying what anyone "should" do but rather what does happen, accurately from the sensor locations on one particular boat.
And a very subtle dig at the amount of perceived wisdom bandied about on these forums with often little attempt made to check if it is actually how the real world behaves ;) ;)

Next, graph number of cat videos on youtube against takeaway pizzas ordered on a friday night- could be a correlation... :)


nF15rXb.png
 
Colvic Watson said:
Nope, we have a 85hp fresh water cooled diesel and it runs cooler at 1800 RPM than at 1500 RPM, but after that it's cooler again. The throughput of seawater is pretty huge at 1800!
Click to expand...

It may run cooler at 1900 RPM, after it has reached running temp', but it will warm up quicker at raised RPM with the prop engaged. See paragraph 2 of your quoted text and the previously posted graphs.
 
What seems to have been lost in this thread is the reason why a warm up period is desirable.
Basically there are various metals used in an engine which have different rates of thermal expansion and different heat capacities.
This means that different parts will take different amounts of time to warm up to operating temperature and during that time they may be at sub optimum for size in relation to each other.
Think for example a piston that warms quickly expanding relative to a bore that takes longer to come to temperature.
Meanwhile the oil film that is meant to keep the moving parts apart is compromised because it is specified to give appropriate performance at operating temperature.
When you apply resistant load to the engine, the reaction forces force the piston to one side of the bore and the con rods apply force to the crankshaft. If the clearances are sub optimal because the engine is not at normal operating temperature, and the lubrication film is likewise suboptimal, then rapid wear will occur.
So attempting to accelerate the warm up process by apply load to the engine is to fundamentally misunderstand the reason for having a warm up in the first place!

NB: Extended low load running for diesel engines is not desirable, but is not what we are discussing here.
Regards
PS I am not just a mechanical engineer, but spend most of my time programming plant automation software. As such i love the trend charts that started this thread.
 
PaulRainbow said:
Doesn't matter by how much, it is quicker :)
Click to expand...

Does quicker actually matter given KiwiJ's apparently knowledgeable comments above?
(Thanx to the Kiwi!)

Is it worth it having it in gear to warm up for the sake of a few minutes?


So attempting to accelerate the warm up process by apply load to the engine is to fundamentally misunderstand the reason for having a warm up in the first place!
Click to expand...
 
Last edited:
Quoting "So attempting to accelerate the warm up process by apply load to the engine is to fundamentally misunderstand the reason for having a warm up in the first place!"

I don't disagree that a warm-up is a good thing, but I have in mind a minute or so, not twenty minutes, on a boat long enough to untie lines or drop the mooring strop. I don't start my car and immediately use full revs/power: I keep revs mostly below 2000 for about half a mile.

Starting followed by long tickover is probably worse for the engine than engaging gear and getting moving immediately. I have posted before about a (Volvo) boat engine I met with 800 hours use that was a pig to start, produced a constant smokescreen when it did run, and needed a bores-honed rebuild - ".....I've never ever run it hard...." the owner said.
 
jwilson said:
Quoting "So attempting to accelerate the warm up process by apply load to the engine is to fundamentally misunderstand the reason for having a warm up in the first place!"

I don't disagree that a warm-up is a good thing, but I have in mind a minute or so, not twenty minutes, on a boat long enough to untie lines or drop the mooring strop. I don't start my car and immediately use full revs/power: I keep revs mostly below 2000 for about half a mile.

Starting followed by long tickover is probably worse for the engine than engaging gear and getting moving immediately. I have posted before about a (Volvo) boat engine I met with 800 hours use that was a pig to start, produced a constant smokescreen when it did run, and needed a bores-honed rebuild - ".....I've never ever run it hard...." the owner said.
Click to expand...

I have suggested previously that slow warm-up is probably the major cause of bore glazing, rather than simply running for extended periods at tickover. Industrial engines run for weeks on end at tickover speeds and do not suffer glazing. Starting from cold at low revs results in condensation of wet gases on the bores, which when heated as the engine becomes hot dries, leaving a varnish-like deposit. This is a well-known phenomenon in reciprocating gas compressors, which can operate under very similar process conditions.
 
You must log in or register to reply here.

Share this page

Top