Daft Diesel question 2. Engine hours

[Twister_Ken]

My boat has an engine hours meter and requires engine service every x hours. This seems to take no account of whether the engine is barely ticking over, or is operating at full steam ahead Mister Parker. Surely 100 hours at say 900 rpm creates a lot less wear/oil degradation/etc than 100 hours at 3000 rpm? Therefore should stuff be serviced more frequently after higher speed operation, or less frequently after poodling around at low revs?

Or (fascinating this) does the engine hours meter actually tot up total revolutions, rather than running time?

 

[bobhunt]

total revolutions

 

[vyv_cox]

You could argue that hours at 900 rpm are considerably more arduous for the engine than hours at 3000, due to likely generation of condensates and overall harm done by very low temperature operation. Probably doesn't make a huge difference to most users as they don't complete x hours in a season and change it at haul-out anyway.

My hour meter definitely measures hours. I bought it 11 hours and 35 minutes after fitting the new engine and connected it to volts for that time to let it catch up.

 

[DownWest]

No to the second question, just hours. Modern cars (BMW) do work out the driving style and adjust the services accordingly. Never heard of this on boats. Most boats run at fairly constant RPM so hours are a good measure of service interval. If you let it idle a lot or use it for charging (both not recomended) then yes, reduce the oil change period. As often mentioned, running at light loads can `glaze´the bores. Leading to loss of compression. Running at medium to high load for long periods is much better than poddling around.This leads to acid built up in the oil with the resultant problems. As I understand it most yacht engines don´t wear out,but are changed for corrosion related problems.
Andrew
I am a slow typist so missed the second 2 posts. Mechanical rev counters measure hours on light aircraft not revs, suprisingly. Some diesel ones use vibration to measure, again hours. If tot revs are used I just must be a bit out of date-A

 

[gandy]

[ QUOTE ]
Or (fascinating this) does the engine hours meter actually tot up total revolutions, rather than running time?

[/ QUOTE ]
Mechanical hour meters, typically built in to the rev counter on older machines, read total revolutions. For example on our MF35 tractor the hour meter specifically said "Hours at 1500rpm".

In contrast our Tiny Tach on the boat reads number of hours that the engine has been running, irrespective of speed. Other electric/electronic ones may read hours that the "ignition" is switched on for, irrespective of whether the engine's even running at all.

 

[KenMcCulloch]

I think more importantly it takes no account of the difference between 1/2 hour to get out of harbour then sail, and the same at the end of the day, times days sailing, vis-a-vis the same number of hours continuous running which should be far less wearing for the engine.

 

[jerryat]

I work on engine hours only. I take the manufacturers recommended oil change/service period and halve it. Ok, it means the engine is a bit spoilt, but what the hell, filters and engine oil cost next to nothing compared with the coat of a new engine. /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif

Friends do similar, but change only the oil at the 'half-service' periods and there's nothing wrong with that. /forums/images/graemlins/smile.gif

 

[Marsupial]

In general long periods of hards use are better than short periods of any use. Short periods of light use are the worst thing you can do to an engine, SO if thats the usage it needs more regular oil changes - IF you change tyhe oil more frequently than the makers reccomendation then usually you can stick to their schedual for filter changes.

Hour meters measure hours.

odometers count revolutions and translate it into miles or kilometers

tachometers (often known incorrectly as "rev counters") indicate the rate of revolutions per minute

 

[DownWest]

The mechanical rev counter on the Piper Cub would record hrs. but only above about 1200 rpm. i.e. when flying. And it was hours, not tot. revs. Similar (but newer!) meters were fitted to more modern plans.
Andrew.

 

[bazobeleza]

I have 2 engine hours meters, both record differing times from the log, /forums/images/graemlins/confused.gif on a recent long trip 160hrs in log, with the meters showing 230hrs & 195 hrs respectively.

now I just use log hours to decide service intervals

 

[reeac]

The traditional electric ones definitely count hours and not revolutions. I once advanced one to a round number of hours when it was out of the boat by connecting it to a 12 volt battery and leaving it for the requisite time on our kitchen window sill.

 

[Bodach na mara]

I log the engine hours and keep a running total. I rarely exceed 70 hours in a season, thus servicing once per year is slightly excessive. but I always service before laying up. As the service interval is 100 hours, I have never needed to service mid-season. I suspect this is common for saily boats.