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Author Topic:   The Metaphysics of an Hour Meter
contender posted 01-29-2007 09:22 PM ET (US)   Profile for contender   Send Email to contender  
Not trying to be funny but why do people want an hour meter
Chuck Tribolet posted 01-29-2007 11:22 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
My service manual specs doing stuff every so many hours. Just
like your car's owner's manual specs changing the oil every
7000 (or whatever) miles.

I'm amazed that the outboard makers don't put one under the


JayR posted 01-30-2007 08:59 AM ET (US)     Profile for JayR  Send Email to JayR     
One manufacturer keeps track of the hours on the motor but you still need a gauge or PC/Palm to read it. It's a step in the right direction....

Having it displayed on the motor so it can be seen at a glance would be a great thing. Particularly to a purchaser of a used motor....

JMARTIN posted 01-30-2007 12:21 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
I have always considered an hour meter to be a motors odometer. How many hours have I ran these plugs? I have 600 hours on my motor. If it had 1200 hours on it, I would look at it differently. John
aja posted 01-30-2007 03:45 PM ET (US)     Profile for aja  Send Email to aja     
My boat didn't come with one but I added it the first season I owned the boat. However, one thing I did do was make a simple stainless bracket and mounted it with the meter inside the console. Although it is a great item to understand maintenance and wear on the engine, you only need to look at it occasionally and opening a panel in the console works fine for that.
contender posted 01-30-2007 10:40 PM ET (US)     Profile for contender  Send Email to contender     
I understand the service mannual, but I take care of my engines I change the water pump about every three years with the lower unit oil, I check them both every year, plugs I change about every two years, I grease my fittings, steering, trailer, and bearings on a regular bases. Fuel filter gets changed once a year, I even pull the prop and grease the spline. JayR how do you know if the hour meter was hook up all the time/ working? Buying a used engine I would check the compresson and how good the water pump was pumping, this would tell me if the person took care of it, I do have a water pressure gauge on my console...thanks
jimh posted 01-30-2007 11:13 PM ET (US)     Profile for jimh  Send Email to jimh     
Normally the SMALL BOAT ELECTRICAL discussion concerns itself with the physics of an hour meter, and this discussion originally was on that topic. We have dispensed with that portion of our discussion of hour meters--their electrical operation is extraordinarily simple and straightforward--so now we turn to the meta-physics of the hour meter. Not the "how" but the "why" of an hour meter.

The hour meter is simply a convenient way to record the approximate operating time of the engine. It relieves the operator from keeping a log of engine time.

I thought the discussion of what color wire should be hooked to the hour meter was somewhat uninspiring, but I think this discussion has outdone that one.

Let's get this out of our system, and then I will delete this discussion, too.

Chuck Tribolet posted 01-31-2007 09:51 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The hour meter clicks and moves every few seconds. If it
quits, it's detectable.

I was out Saturday on a friend's whaler and we were discussing
engine hours. He doesn't have an hour meter and said he was
running about a 100 hours a year. I pointed out that my hour
meter clocked 90 hours a year, he goes out more days than I
do, and he goes farther than I do. I had no trouble convincing
him he was running at 150 hours a year, maybe 200.


where2 posted 01-31-2007 07:46 PM ET (US)     Profile for where2  Send Email to where2     
It reminds me how little I actually use the boat. When I spend more time commuting to and from work in a month than I use the boat in a year... That's why I have an hour meter. It's an excuse to use the boat more!
jimh posted 02-03-2007 11:00 AM ET (US)     Profile for jimh  Send Email to jimh     
I think where2's observation is very acute. I explain:

After what I thought was a very active season of boating wherein we had made as much use of our boat as we thought possible, my hour meter informed me the engine had only run for about 65-hours. This seemed ridiculously low, and I vowed to make more use of my boat next year.

On this basis, I see the hour meter as a subtle inducement to greater boating.

Hal Watkins posted 02-03-2007 01:24 PM ET (US)     Profile for Hal Watkins  Send Email to Hal Watkins     
As a long time pilot I have operated many aircraft with a "Hobbs" meter. It appears to be an hour meter but it functions based on a preset RPM. Example: If cruise were 2400 RPM, then at a constant 2400 RPM a "hobbs" hour is an actual hour but at 2200 RPM is takes 1.1 hours to accumulate an hour on the "Hobbs". It is used by aircraft rental companies so that the 20 minutes on the ground, taxi time, is not charged at the same rate as the full power and cruise time. As a rentor I didn't feel like I had to get in the air quite so quickly. I suppose from a maintenance standpoint it allowed for a relative "load" factor. So, trolling and no wake time wouldn't present the same preventive mainenance and oil change demands as cruise time. Is a "Hobbs" meter relative in a boating environment? Hal of Waseca, MN
jimh posted 02-03-2007 02:57 PM ET (US)     Profile for jimh  Send Email to jimh     
As far as I can tell, all hour meters record actual time. They all work on an electrical basis. When the proper voltage is supplied, the hour meters run and accumulate a running time total. I have never heard of an hour meter which recorded time at some ratio to actual time, at least not intentionally.

If there is a variation between the amount of time an engine is actually running and the amount of time accumulated on its hour meter, this is probably due to the mechanism which is chosen to actuate the hour meter.

The typical arrangement to actuate the hour meter is via a switch. There are many possibilities for actuating the switch:

--the hour meter is directly wired to the ignition switch of the engine, in the ON or RUN position; this accumulates time even if the engine has been shut off or stalled. As long as the ignition switch is in the ON position, the hour meter turns. This is the most common application in an outboard-powered boat which has a two-stroke engine. It is possible to leave the ignition switch in the ON position after engine shut off, and the hour meter may accumulate time during which the engine was not actually running.

--a switch linked to an sensor that provides positive indication of engine operation. A common choice in an engine with an oil sump and forced oil lubrication is to link to a pressure switch in the oil system. The presence of oil pressure is taken as an indicator that the engine is running. The hour meter would only record the time the engine was running, or at least running with oil pressure.

--a switch linked to a sensor outside the engine. For example, in an airplane you could link to an airspeed sensor. The hour meter would run only when the airplane's air speed exceeded some threshold. The hour meter would only record the time the plane was actually airborne. Engine time on the ground would not be recorded.

--a switch linked to the engine in some way which set certain thresholds for engine speed before actuating. For example, a switch which only closed if the engine speed exceeded a particular RPM. I am not aware of any such switch, but it would be possible to implement such a switch if desired.

In modern outboard motors, such as the Bombardier Evinrude E-TEC, the engine management module tracks the engine running time. If further tracks the engine speed range as a function of time. It stores all of this information and provides it to the engine owner via a serial data link. It also formats and presents the data in a very easy to interpret graphical form. With a modern engine like the Evinrude E-TEC the need for an hour meter is reduced.

See the REFERENCE article on the E-TEC Engine History Report for more information on how a modern engine records its operation:

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