Changing Engine Oil
by Don Casey
Engine manufacturers typically recommend an oil change every 100 hours,
and at least once a year. Even if your engine manual allows for a longer
interval between oil changes, changing the oil more often will extend
the life of the engine.
One hundred engine hours between oil changes is fine for gasoline engines,
but diesel engines are much harder on their lubrication. You should
change the oil in a diesel engine about every 50 hours. The shorter
interval is especially important for sailors who use their engines for
only an hour or two per outing. Dirty oil sitting idle becomes destructive
to the internal surfaces of the engine. If your boat will be idle for
a while-over the winter, for example-it is imperative to remove the
contaminated oil and fill the engine with clean oil.
Unfortunately regular oil changes are more often the exception rather
than the rule, mainly because changing the oil in a boat engine can
be a difficult and messy job. While it takes only a minute to drain
the oil from an automobile engine, the oil drain plug in a boat is most
often either out of reach or non-existent. And even where the plug is
accessible, there is usually inadequate space beneath the engine for
a container to catch the draining oil.
The trick to hassle-free oil changing is to find a method that works
for your engine installation. Here are some possibilities.
Through
the Drain Plug
A foil roasting pan from the supermarket may fit beneath your engine
to provide a container to catch the old oil. Check the pan's capacity
with water first to make sure it will hold all the oil. Foil pans tend
to buckle when full, so put a piece of thin plywood under the pan to
keep the bottom rigid. Spread an oil-absorbent cloth beneath the pan
to catch the inevitable splash or spill.
You can drain the oil into a plastic garbage bag if you band the mouth
of the bag to a tin can with both ends removed. A pineapple can works
well in restricted space. Hot oil tends to seep through some plastics,
so use two heavy-duty bags, one inside the other.
Replacing the drain plug with a hose fitting and a length of hose allows
you to "decant" the oil into any container you can get lower than the
engine sump. Kits containing hose and fittings are available, or you
can assemble your own with a threaded hose barb and oil-resistant hose.
Be sure the threads on the barb are the same as on the plug. Clamp a
second barb to the free end of the hose and fit it with a cap (or a
plug). Rig a hanger to keep the end of the hose well above the oil level,
except when you are draining the oil.
Where space lower than the engine is inadequate for a container, use
a similar hose connection between the drain plug and a brass piston
pump to pump the oil out of the engine. Mounting the pump permanently
to an engine-compartment bulkhead makes oil removal as easy as giving
the handle a few strokes. If you don't object to the expense, substituting
an electric pump-one intended for hot oil-reduces oil draining to flipping
a switch.
Through
the Dipstick Tube
Many marine engines simply don't have a drain plug, or it is too inaccessible
even for a hose connection. Draining the oil from these engines requires
a pump to suck it out through the dipstick tube.
On some engines the dipstick tube is threaded. The supplied oil-change
pump screws directly to the dipstick tube and the oil is removed with
a few pulls on the handle. This works fine where there is good access.
Otherwise, you can mount the pump to a convenient bulkhead and connect
it to the dipstick with a hose with threaded fittings-essentially a
very short garden hose. Mount a short length of PVC pipe fitted with
a male hose adapter next to the pump to provide a place to "park" the
hose when not in use.
Where the dipstick tube is not threaded, you have to use a pick-up tube
inserted through the dipstick tube to extract the oil. Most pick-up
tubes furnished with oil-change pumps are unnecessarily small. Replacing
them with 1/4-inch (ID) copper tubing changes this common method of
oil removal from agonizing to amazing. Be sure the tube is long enough
to reach the bottom of the engine oil pan, and connect it to your pump
with a length of rubber hose. Again, mounting the pump to a bulkhead
eases the process. Also mount a length of PVC pipe, capped at the bottom,
to sheath the pick-up tube.
Run
the Engine
Before you begin an oil change, the engine should be hot. Warm oil is
easier to suck through a rubber hose or copper straw, but the reason
for running the engine is more essential than that. You are changing
the oil because it is contaminated with abrasive and chemical impurities.
But the dirt in oil is just like dirt in water; leave it undisturbed
and it settles to the bottom. Suck out the cold oil and much of the
dirt stays behind, immediately contaminating the fresh oil and defeating
the whole purpose of the oil change. Run the engine and get all of the
contaminants in suspension so they come out with the oil.
If you are pumping out the old oil, the most convenient receptacle is
probably a plastic milk jug. The small opening will keeps the outlet
hose under control, and the capped jug is convenient for transporting
the old oil to the reclamation receptacle in the marina or at a nearby
service station. If your pump isn't mounted to a bulkhead, wrap a thick
towel around it to keep from burning your hands when you start sucking
hot oil through it.
Use a socket wrench to remove the drain plug, and as soon as the plug
is loose enough to turn by hand, remove the socket from your ratchet
and put it on a short extension. Used like a nut driver, this will let
you remove the plug without dropping it into the container.
Change
the Filter
Regardless of manufacturer's recommendations, change the oil filter
every time you change the oil.
Virtually every other filter you will encounter sits vertically so the
fluid it contains does not spill when the filter is opened, but for
some reason that totally eludes me, engine designers mount oil filters
at an angle, horizontally, even upside down. You can guess what happens
when you open them. For all but the upside down variety, you can contain
the spilling oil by slipping a freezer bag over the filter and unscrewing
the filter inside the bag. Bag it before you break the seal.
Most oil filters are the "spin-on" variety. You need a strap wrench
to remove them. Strap wrenches grip the canister when pressure is applied
to the handle. If the wrench slips, take it off the filter and reverse
it; it only works in one direction. Coat the gasket of the new filter
lightly with oil before screwing it in place. Hand tighten it until
the gasket makes full contact, then tighten it another 3/4 of a turn.
Some older engines are equipped with cartridge type oil filters. A center
bolt typically holds the filter housing in place. Release the bolt and
remove the canister. Empty it and discard the old cartridge. Clean the
housing with diesel fuel (or kerosene) and insert the new cartridge.
If a separate sealing ring is included with the cartridge, carefully
pry the old seal out of its seat by pricking it with a straight pin.
Coat the new seal with oil and push it into position. Reinstall the
canister.
Pour
in Fresh Oil
The last step in every oil change is pouring in the fresh oil. Your
engine manual will give you the viscosity and API rating for the oil
recommended by the manufacturer. Screw-top containers make it simple
to pour the oil into the filler opening on top of the engine, provided
there is ample room to turn up the container. If not, you can avoid
a lot of irritation by using a funnel and a piece of hose and to get
the oil from the container to the engine. Clamp a wire hook to the end
of the hose to hold it inside the filler opening.
Make generous use of oil-absorbent pads when draining and filling engine
oil. Remember that even a sheen on the water from your bilge pump discharge
can cost you dearly.
For more
information about boat maintenance, consult This Old Boat by Don
Casey.
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