158 seamanship secrets
disconnect the hose, then momentarily open the seacock. If the fl ow is reduced
or absent, there is an obstruction outside. If the fl ow is healthy, the problem
must be upstream—perhaps in the raw-water pump (see below).
Cooling System Maintenance
Replace the raw-water impeller. Th e raw-water system pulls in seawater through
a vane-type pump called an impeller pump. Over time the rubber vanes, or impel-
lers, harden and crack. Keep a spare impeller onboard. Change the impeller once
a year to prevent problems.
Change the drive belts. As mentioned above, these drive your shaft,
alternator, and water pump. Change all belts once a year.
Adjust the stuffi ng box and replace the packing. Packing comes by the roll
or in preformed rings. It’s made of square-sided rope and used to fi ll the void
between the shaft and shaft tube to seal out water. Replace the packing annually,
or get the boatyard to do it for you.
THE LUBRICATION SYSTEM
Oil works as hard as or harder than any other fl uid circulating through a diesel
engine. It must lubricate parts, cool the engine, and trap dirt and grime. Without
oil, vital parts would seize up and melt together, and the engine would cease
operating. Contaminants would clog injectors and gum up cylinder walls, and
the engine would surely overheat. Transmission fl uid lubricates the hardworking
parts of the gearbox for smooth, trouble-free shift ing.
Lubrication System Checklist
Check the oil level and condition (before start-up). Time and again I see
skippers start their engines without taking the few seconds to pull the oil
dipstick. Th ese skippers are missing two important clues as to what’s going on
inside their engines. First, you need to know if there’s enough oil in the oil pan,
or sump (the oil reservoir in the bottom part of the engine). Th e manufacturer
puts those marks on the stick for a reason, so top it up if it’s low. Second, you
need to know the condition of the oil. If the dipstick readings are getting so
dark that it’s diffi cult to see the stick, this indicates that your oil is losing its
ability to trap carbon, soot, and sulfur. Oil stops these villains to help the
engine run cooler.
Check the oil pressure gauge and oil pressure warning light (aft er start-up).
The gauge should read normally and the warning light should be out.
Check the transmission fluid level (before start-up). Look for the trans-
mission gearbox on the back of the engine near the shaft coupling. Unscrew
the dipstick on top of the gearbox. Make sure the fluid is clear; a milky color
indicates water intrusion. Wipe the stick clean and reinsert it into the hole
without screwing down the top. Pull it out and check the level. It should read