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How do engine "hours" work?

Discussion in 'Carver Yacht' started by bluestar, Mar 9, 2012.

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  1. bluestar, Mar 9, 2012
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    bluestar

    bluestar New Member

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    Amateur question. How is engine "hours" used as a measure of engine? Is it simply how much time the engine is turned on?

    I am puzzled about this because a boat running at low speed for an hour, should have much less wear and tear on the engine than running at max speed. Is that not the case?
  2. Capt J, Mar 9, 2012
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    Capt J

    Capt J Senior Member

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    Yes and no. Engine hours record how many hours the engine has run. On older engines it's the only way you can judge it. Running at low speed for many hours can create as much wear as at cruise. On the newer electronic diesels, a lot of manufacturers are using total fuel used and engine hours to determine life and such.
  3. YachtForums, Mar 9, 2012
    #3
    YachtForums

    YachtForums Administrator

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    I have to admit, when I saw this question in the New Posts list, I rolled my eyes. Truth is, it's a good question and Capt. J posted a good answer. I just had a buyer look at one of my boats, an outboard powered sport deck boat with a pair of Merc Opti's. We took it to a Merc mechanic who plugged in a laptop and it gave the exact RPM range of operation and number of hours over the life of the engines. Sure enough, of the 350 hours on these engines, 320 of them were below 3500 RPM's. Why? $5.00 fuel!
  4. Pascal, Mar 9, 2012
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    Pascal

    Pascal Senior Member

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    Indeed if you look at official service intervals on modern diesels they are listen in hours or gallons.

    Now, gallons may be hard to track.. For instance some CAT displays (2002 vintage) sometimes jump around for no reasons so unless you keep track of fuel burn in the logs, the actual number shown on the display may be way off. Although the numbers shown in the ECU when the surveyor plugs his computer in mayb be accurate
  5. bluestar, Mar 18, 2012
    #5
    bluestar

    bluestar New Member

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    The 83 Carver 36 I'm looking at has engines with 1200 hours on them. At first it seemed a shockingly high number to me, since I usually only run my other boat's engine about 20 hours the whole season.

    I had a mechanic do a compression test on the engines; the results are good. Anything else I need to do to ensure the engines on this new old boat has no existing issue?

    It seems to me the most accurate measure of boat engine wear and tear, is how many revolutions the engine had turned....
  6. Marmot, Mar 18, 2012
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    Marmot

    Marmot Senior Member

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    It could have spent all of its very short life idling at low rpm or screaming at high speed with no load, or operated overloaded for who knows how long. That is why total fuel burn and hours is the current technique to measure how much life it has used.

    Counting revolutions is only useful for calculating slip.