Engine makers advise checking the oil level before every start, and in fact, you cannot check it too often. That said, if you have checked the oil might be tempting to skip checking it before the last autumn outing. Any change in the oil level is cause for concern. If the level is too high, it is likely that coolant has gotten into the oil, which can damage the engine instantly if you try to start it. If the oil level is below the low mark on the dipstick, there is likely a leak that will surely continue after the engine starts.
Some engines seem to lose their first half quart of oil rather quickly, after which the oil level stays constant at the low end of the range marked on the dip stick. Those dip stick high and low marks were set at the factory, assuming a level engine, and sailboat engines often tilt 15 degrees or more, which can distort the oil level. Adding oil to the high mark might then overfill the engine.
As important as the level of oil, or even more so, is the general appearance of the oil and of the dipstick. Look for any evidence of contamination caused by poor combustion, wear, or leakage.
the
oilCoolant in the oil can look like a gray Coolant in or milky emulsion or it can look like coolant. If someone poured coolant into the oil filler, the engine must be drained and flushed clean. Other possible sources of coolant in the oil—cylinder head gasket, cylinder head, block, or cylinder liner—are all even more serious.
crystals on the dipstick. Water in the oil Any raw water might have come in through the exhaust system,
Fuel getting into the oil will raise the Fuel in oil level, thin the oil, and impart the the oil distinctive smell of diesel fuel. Most likely sources are the injector pump or the lift pump.
Metal or
soot in
the oilSmall bits of metal in the oil are most easily seen when you change it. They can come from almost any surface that the oil the oil lubricates. You must find and correct the problem before running the engine. Soot in the oil will make it look dirty and black, which indicates poor combustion. Sludge, in contrast, most likely indicates that an oil change is long overdue.
Engine makers advise changing the oil every 50 hours or so and, as with reading the dipstick, you cannot do this too often. There are synthetic oils whose makers claim that they can be used indefinitely without changing. Even so, every engine runs better with fresh oil.
How to
change
the oilTo change the oil, first run the engine How to up to operating temperature and stop it. Put a plastic baggie over the (hot!) oil filter, stuff a wad of paper towel under the filter, and remove it using a filter wrench if necessary. Changing the filter is perhaps more important than changing the oil itself because the filter contains a bypass that will shunt gets clogged.
bypass that will shunt How to change the oil unfiltered oil back to the engine once the element gets clogged.
Rub a film of oil onto the new filter’s gasket and screw it on firmly but not too tight. Next, drain the old oil or pump it out through the dipstick opening. Some of the available oil pumps work much better than others. Those that develop a vacuum are somewhat easier to use but much larger and therefore difficult to stow aboard. A simple transfer pump can work well if it is a good one and fitted with a thin copper tube long enough to reach the bottom of the oil pan.
Add fresh oil no higher than the level marked on the dipstick, allowing time for all the oil to drain down before checking the level and allowing, also, for the capacity of the filter. If you have an oil pressure gauge, prime the oil filter by closing the raw water intake, engaging the engine stop control, and cranking the starter for two or three 10-second intervals a few minutes apart until oil pressure appears, then re-open the raw water intake. Run the engine briefly, stop it, and once again check the oil level.
An oil filter that installs with the gasket surface horizontal and facing up is best because you can prime a new filter by pouring oil into it before screwing it on and it will not leak as much oil when you remove it. If the engine maker did not design it this way, consider installing a remote oil filter that is easily accessible and properly oriented. Go oversize, while you are at it.
Oil
grade
and
weightThe engine maker will say, in the manual, precisely what grade and weight (quality) and weight (viscosity) of oil to use. CF-4 is the lowest grade suitable for
grade and weight marine diesels. The C denotes “commercial” grade and the F might also be a C, D, or E (these three are older, obsolete grades that the CF-4 grade replaces) or a G, H, I, or J, depending on emissions handling and level of sulfur in the fuel. Inferior designations begin with S, which denotes “service” grade, and are only for gasoline engines. The 4 denotes a 4-stroke engine. Oil weight is typically two numbers, both divisible by 5, in the form 10W-30, where the first number can be as low as 0 or 5 and the second can be as high as 50. The first number is the cold starting viscosity in winter, hence the W. The second number is the viscosity at normal operating temperature. When topping off the oil level, try to add only the same brand, grade, and weight of oil as before and thereby avoid mixing two different additive packages. Starter Engine starters can be pre-engaged, where an external solenoid kicks the starter drive gear into the flywheel before cranking, or inertial, where centrifugal force throws a Bendix type drive gear into engagement with the flywheel and the solenoid only switches the starter current. Inertial starters are prone to corrosion and Bendix gear wear. Pre-engaged starters tend to fail when the solenoid wears out. Failure to start most often results from low voltage at the starter terminal, which needs at least 80% of battery voltage, so check that first.