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  1. #1

    Default Have I ruined my genset?

    To charge the batteries on my sailboat, I have a single-cylinder, 7-horsepower Kubota diesel driving a 150-amp Leece-Neville alternator. It works pretty well, doesn't use much fuel, even if it is on the loud side. It has slightly over 2,100 hours on it, has never overheated and gets an oil change regularly every 100 hours.

    However, I seem to have developed a lot of crankcase pressure as not long ago the engine blew the dip stick out (made quite a mess but I was able to stop the engine before it lost oil pressure - it only lost about a quarter of its capacity). The engine always starts quickly and doesn't use any oil between changes.

    Since the engine just has a manual throttle, I've always set it to the wide open position, as the alternator is a big load when when bulk charging the batteries. I suppose I should be reducing the RPM when the regulator goes into the absorption mode but I never have. Do you think that running the engine at full throttle with a light load has created the crankcase pressure? I'm not lazy but continuously adjusting the RPM while I'm charging the batteries isn't my idea of fun.

    I'm grateful for your thoughts.

  2. #2
    Join Date
    May 2015

    Default Re: Have I ruined my genset?

    Common in small generator engines is the glazing of the cylinder walls when run at light loads at high speed for many hours. Diesel fuel helps lube the rings. At high speed/no load very little diesel is sprayed yet the rings are moving rapidly. Glazing causes increased crankcase pressure, oil burning, oil in the exhaust and so on. Sometimes the pressure is enough to blow out the seals. The fix is to hone and recross hatch the cylinder and install new rings. Usually standard size. Sometimes if the cylinder is really worn, oversize rings. Pic of Detroit sleeves is to show what proper cross hatching looks like. The angle should be around 45. These light grooves allow the rings to carry a small amount of oil to the top of the cylinder for lubrication. Once the grooves are worn away everything wears fast.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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