When a boat is out of the water, it must be hooked up to a water source to run the engine in order to allow for proper cooling and systems operations of the boat engine. Failure to do this can cause damage to the engine.
The muffs will be slid in place on the outboard section of the engine in position so the muffs cover the water-intake ports. The muffs will then be hooked up to a hose with running water turned on to allow a water source to reach the water-intake valves.
These systems are commonly used when performing maintenance on boats that requires them to be out of the water, yet still need to have the engine run during the maintenance operations. In an effort to avoid corrosion, some salt water boaters use this system to flush their engines of salt water when they remove their boat from the water as a preventative maintenance consideration.
Flushing systems are regularly used when winterizing a boat in cold-weather climates. Maintenance operation will run anti-freeze liquid instead of water through their system to help avoid freezing of the engine systems through cold weather periods.
When using these systems, it is advised that engine rpm not be brought up to higher levels. In most cases, a limited supply of water is available through a hose system and higher-demand operating levels can lead to overheating of the engine and other potentially damaging conditions. Low engine settings should be used when conducting operations using engine "ears" or an engine flushing system.