On many Johnson and Evinrude outboards, pushing the key in while cranking opens the primer solenoid. This sends extra fuel through small hoses to the intake manifold. The red lever on the solenoid opens it by hand, which is useful for priming the engine and for testing it.

A solenoid with an open circuit coil won't add any fuel, so the engine will be hard to start from cold. A worn valve seal lets fuel leak through when it should be closed, which can make the engine run rich or flood. The following video shows an electrical test of the solenoid, a pressure test of the valve seal, and installing a repair kit.