There should be a law that boat designers should be forced to service their own boats. That might make common maintenance tasks, like changing engine oil, a little easier. In most inboard or I/O engine installations, changing engine oil is looked on with the same fervor as going to the dentist.
Most marine engine manufacturers recommend changing engine oil every 100 to 200 hours of operation or at least annually. Frankly, most marine engines aren’t used often enough to cause any appreciable amount of breakdown in the oil. However, the marine environment means that there may well be moisture accumulating in the idle engine. Changing engine oil on a regular basis (as well as the filter) will help prolong the life of your engine.
If you are one of the lucky ones who can get a drain pan under the engine and easily drain the oil, consider yourself lucky and retire to the bar. For the rest of us, we’ll cover various methods of draining the oil, from simple to complex.
Make a few simple preparations before changing oil, regardless of how simple or complex your oil-changing method is. The first step is to properly warm up your engine. There are several reasons for this. First, warm oil is easier to drain out of the engine. Second, the whole reason behind changing the oil is to get all the contaminates out of the engine with the oil. Running the engine puts all the crud that settled out in the bottom of the oil pan back in suspension in the oil.
Make sure you have enough containers to hold all the old oil. Many people use old plastic milk jugs to hold the oil. Tight fitting tops lessen the likelihood of a messy spill. Have a good supply of oil absorbing pads ready to deploy around and under the engine. Have enough of the right grade of oil and the proper filter at hand. Don’t forget the filter wrench.
The simplest oil change systems are manual pumps that access the engine oil through the dipstick tube. A small flexible tube is snaked down the dipstick tube to the bottom of the oil pan and the oil is then sucked out.
There are three main styles of manual pumps readily available at your marine store. The first is a metal container with a pump attached. The pickup tube that goes into the pickup tube fits into a larger tube with a pinch clamp. This clamp seals off the hose and allows the pump to build up a vacuum in the metal container. When the clamp is loosened, the vacuum sucks out the oil.
These pumps are simple, well built and last for years. The downside is that the capacity o the container is limited and may require emptying during the course of an oil change. The pickup tube is easily snaked down the dipstick but is a little on the small side, resulting in a slower flow of oil.
There is also a plastic bodied manual pump. This pump has a direct action in that the handle is moved up and down to directly suck the oil into the plastic container. This means you don’t have to stop and build up a vacuum as in the pump mentioned above. However, Like that pump, capacity of the container is limited and may require emptying during the course of an oil change.
The last style of pump is a handheld piston pump. This pump has a pickup hose that either screws onto a threaded dipstick tube or is snaked down through the tube and an output hose. In fact, it looks like a small version of a handheld bilge pump. The output hose is directed into a container (milk jug?) to hold the oil while the pump is held and the handle pushed in and out.
The pump capacity is small, making the oil change a long and tiring effort. The loose output tube stuffed into a jug is a mess just waiting to happen. You did put oil pads under the jugs, didn’t you?
Okay, the manual pumps sound like a lot of work, so let’s see what electricity can do for us. The simplest electric pump is the drill pump. The pump uses a rubber impeller in a plastic housing to pump the oil. The motive power for this style pump is a drill. You tighten the pump shaft in the drill chuck and turn it on.
Of course, you have the input tube stuck down the dipstick tube, the output tube stuck into a jug, the pump body in one hand and the drill motor in the other. See any potentially messy problems here? One other caveat, make sure the impeller in the pump is rated for petroleum products; some pumps are only rated for water.
Pumps mounted on buckets are a step up from the handheld drill pumps. These have a (usually) 12 volt impeller pump mounted on the lid a of a three to five gallon metal or plastic bucket. A power cord with alligator clips on the end allows the pump to be connected to a 12-volt battery for power. Most have on-off switches and some have reversing switches so the contents of the bucket can be pumped out.
The input hose can be a type that screws onto a threaded dipstick or have a tube to snake down through the dipstick. There are a few nagging problems with this style of pump. Empty, they are top heavy and hard to store. Some users solve this problem by keeping the pump in a plastic milk crate for stability. Put an oil pad in the bottom of the crate to soak up any dribbles. It is sometimes hard to find a stable flat location for the pump in the bilge of the boat and ready access to 12-volt power may be problematic. Filled, the bucket is a heavy object to move around and off the boat.
One refinement in using this system is to replace the oil pan drain plug with an elbow and a length of hose. The other end of the hose comes out from under the engine and can be connected to the pump/bucket. Make sure the hose is rated for petroleum products, can be sealed at the open end and isn’t subject to chafe or wear.
Many larger boats, especially trawlers, have permanently installed oil-changing systems. These usually consist of hoses from the bottom of the oil pans connected to a manifold and pump assembly. This manifold and pump assembly is permanently bolted to a bulkhead.
There are several different models available. Variations allow from one to five or six connections to be drained through the manifold. Why five or six? Twin engines with transmissions as well as gen sets can all be connected to a manifold/pump unit and drained AND REFILLED selectively. When contemplating an oil change on a big Caterpillar main propulsion engine, it’s transmission and a 7.5 KW genset; you don’t want to be thinking about a three or five-gallon portable bucket pump.
Many of these systems are professionally installed but are certainly within the capabilities of a dedicated boater. The pumps, manifolds and connectors are available though most marine stores. The hoses used are 1/2-inch type A petroleum rated hose. Runs over ten feet long should use 5/8-inch hoses. Make sure you have the right oil pan fittings, as there are several different sizes, including metric fittings. Cross threading an oil pan fitting will certainly ruin your day as well as the pan.
No oil change is complete until the old oil is properly disposed of. Many, if not most, marinas have proper places for disposing of old oil. If not, many auto parts stores will also accept used oil free or for a nominal price. Be careful in moving the containers around, you are liable for spills, whether from fuel or oil.
There is another way of disposing of old engine oil if you have a diesel engine, mixing it with the diesel fuel. This is a very controversial subject among the diesel folks, some swear by and others at it. The idea is that you can mix up to 10% old oil in the diesel fuel. The oil should be filtered and well mixed with some diesel before being put into the tank.
It’s probably not a good idea in places with many proper disposal sites. However, if you were on a long cruise or at sea with no proper facilities, it would be better to burn it than dumping it over the side. As mentioned above, it is controversial and not a universally accepted practice.
Other than getting the boat designer to do it, you now have some oil change options. Find what works best for, you, don’t make a mess, dispose of the oil properly and change it often!
Manual oil change pumps
Drill pump (L), Portable electric pump (R)
Bucket mounted oil change pump
Oil change pump designer for permanent mounting
Oil change pump and manifold for changing oil in two engines