Task One: The Oil Change
There are a number of reasons why you should change the oil in your vessel's propulsion engine. As you operate your motor, the lubricating oil gradually wears out. Initially, it becomes dirty or contaminated with combustion byproducts. With each compression, power, and exhaust stroke of each cylinder, gases and liquids, albeit in small quantities, slip by the piston rings and into the crankcase, where the lubricating-oil reservoir is located. These byproducts include unburned fuel, soot, and water (water is one of the byproducts of burning fossil fuels); their presence is cumulative, and they ultimately contaminate the oil. The deep-black color that characterizes most diesel-engine lube oil after it's been used for just a few hours is the result of soot, a byproduct of the combustion process. The soot is abrasive and thus harmful in and of itself. But it also thickens the oil, making it sludgy, which prevents it from traveling into the close tolerances between the moving parts it lubricates. Additionally, the water mixes with the sulfur in the fuel to create sulfuric acid, a compound that will attack polished metal surfaces inside the engine, such as bearings and journals. Oil wears out and ages in several other ways, but you shouldn't need any more reasons to replace it beyond those I've mentioned.