Tough Neighborhood
In the marine environment, corrosion – inside and outside the engine – is a constant threat. A boat engine always operates near the water, drawing in very humid air directly off the water’s surface in order to operate. This humid air also gets inside combustion chambers through open valves when the engine is not in use. And in a saltwater environment that air can be especially corrosive. It’s one of the harshest environments imaginable for an engine.
This humid environment and the low operating temperature of a marine engine combine to make a marine engine more susceptible to formation of condensation in the oil, and to contamination of the oil by unburned fuel. This is especially true if the engine is used for long periods of slow-trolling and never gets hot enough to evaporate condensed fuel and water from the oil. Now consider that when it’s not working hard to get you to the fish, or tow you around the lake, or carry you to a distant port, a marine engine is often idle for weeks or months at a time, which creates another opportunity for condensation to collect inside the engine. For this reason, Mercury Precision Lubricants oil products contain specific anti-corrosion inhibitors, which simply are not present in automotive engine oil.