[Baz]

Outboard motors use water for cooling.

The water comes in through 'inlets' or ports - at the lower part of the motor - the part that sits in the water.

Those "muffs" slide over the part of the motor where the water 'inlets' or ports are. Attach your garden hose. Turn it on. Now you have water supplied to the motor so it can be run out of the water.

Why run a boat motor out of the water? To flush out the salt water after a day on the sea. Or while doing mechanical work on the motor while it sits on your driveway.

Also - just like a car in storage - the engine or motor should be started and run periodically to keep the fluids and mechanicals in order.