Engine Hours Meter

[JVB]

See Jalepeno's link for the Diesel Tiny Tach. Price listed is $95. Also available from Aircraft Spruce and Specialty for same price:
http://www.aircraftspruce.com/menus/in/tachometers.html

Steve Dion, you are apparently familiar with the simple timer style hour meter. In airplanes that's usually a Hobbs meter.
http://www.aircraftspruce.com/menus/in/hourmeters_hobbs.html
FBO's (fixed base operators) usually rent by the Hobbs hour because Tach hours will accumulate slower during taxi and other low power operating time. The Hobbs time starts when oil pressure goes above about 4 psi and stops when oil pressure goes below 4 psi. Typical oil pressure when a Lycoming is running is 60 to 90 psi.

 

[Benny17441]

An hour meter powered by the key switch should give close enough readings for any application. With a loud alarm buzzer it is really difficult to leave the switch on when the engine isn't running. I use ours to keep track of fuel consumption. Our tank gauge took a dive about three years ago and I'm not thinking of fixing it any time soon.

 

[SailArkansas]

SailArkansas:

I do not want to get into any discussion here about what is right or wrong. I think the article in YanmarHelp was very specific that running your diesel engine for extended periods of time at low RPM's is one of the worst things you can do for it. Just because you have a sweet spot at 1000 - 1200 rpms was not the point that they aurthor of the article was trying to say. These engines are designed to be run at 70-80% of max rated RPM. If you do this and take care of the machine they can be expected to last for 10,000 - 12,000 hrs. If you don't it is your choice.

Steve

I appreciate your input but for every expert on one side of the question there are experts on the other side as well. Just to illustrate my point take a look at the following:

RPM isn't actually your only indication of load. There are actually are others and, in fact, RPM isn't really a good predictor of load. On electronic engines, you can just read the load percentage off of the instrument display. But those of us without electronic engines need a reasonably reliable proxy. Fuel consumption gives a very accurate estimation of the power being produced by an engine. Find the burn rate using Flow Scans or running for a substantial portion of a tank at the same load and then filling. Modern high speed diesels produce 18 to 20 hp per gallon burned per hour and this is a remarkably stable figure across all major brands. Older engines are on the low side of this and newer engines are on the high side. Once you know the HP you are producing, you can check the engine manufacturers curve on what the rated HP is at that engine speed to know percent of load.


There is considerable controversy over slow running. Some think that a diesel is happiest at high load and low load running will destroy them. My observation is hard running and overload destroys many engines. Many folks incorrectly think that reducing RPM and running "200 off the top" is enough to prevent overload. These engines live a tough live and die young. Engines that are lightly loaded last longer than overloaded engines. There is no question on that.

But what you are asking is "How slow can I run before I'm starting to be hard on the engines or negative impact their longevity?" In my view, the slower you run the engines the better as long as the following factors are true:

• The engine must be at full operating temperature,
• You need to change RPMs frequently during break-in period (first 50 to 100 hours)
• Run them up once at end of day to ensure that they reach max normal operating temp.

Light load can cause engines to run cold and this is damaging. Ensure you are at full operating temperature. If you are at full operating temperature, I believe that the lighter you can run, the longer they will last. This will bring some debate, but the commercial boats with very high hour engines are often the ones run at well below rated HP.



My engines spend many hours running at a fraction of full load in that we often cruise around at our hull speed of 7.5 kts. This only requires 30 HP from each engine where they are capable of 270 hp each. Our engines have never caused a problem in 2,900 hours and they will likely go for considerably longer.



If you are at full temperature, you can run them as slowly as you like. Light load is good as long as the engines is at full temperature.


Ok then, which expert do you go with?

This may be unrelated but I have a 94 Corvette that i dearly love. I know guys that drive their vettes hard and fast and claim their built for it. I know other guys that drive their vettes like I do which is just enjoying the way it handles at normal speeds. Guess whose cars are in the shop more?

It just makes sense to me not to run any engine at its full load capability.

Fair winds and good sailing

 

[Stu Jackson]

Bringing the engine up to full operating temperature is consistent in all discussions. Doing so, however, at the end of each day makes little sense, since then is when my manual says it should be allowed to cool down. Why not just run it at the beginning of the day up to temp, and then let it cool down after a short run at the end of the day?

 

[stephen Penny]

Andrew Shemella,

Consider this..... Before you go out the next time top off your fuel tank. Then record the time you are operating your motor This could be multiple motoring events. Then top off your tank, divide the total number of hours motoring by the total number of gallons consumed over that period and you now you know your fuel consumption in hours/gallon. Then start a log of the number of gallons filled and when. That way you will know how many hours your engine operates to establish preventative maintenance frequency. This is what I do since I do not have an hour meter. Last year my 2GM30F Yanmar engine operated 54 hours based on consuming 18 gallons at 3 hours/gallon. I use this information to schedule engine oil changes every 50 hours and other maintenance.

On the other hand, I have waterski boat and fortunately it came with an engine hour meter. I use the meter hours to schedule engine oil and filter replacement and other maintenance.