Ignition Switch 6 Terminals 3 Pos 87-88107 MP41000

Function and technical context

The MP41000 ignition switch is a 6-terminal, 3-position electromechanical switch that governs the ignition system in Mercury and MerCruiser marine engines. It acts as the main control point of the engine electrical circuit, managing three distinct operating states: complete shutdown, accessory activation, and engine start. Its correct switching ensures that current reaches the appropriate components in each phase of operation, from powering instruments and auxiliary equipment to actuating the starter motor. A failure in this switch can prevent engine starting, cause power loss to electrical accessories, or generate short circuits that compromise the entire vessel's electrical installation, with the safety consequences that entails during navigation.

When to replace this part?

The most common symptoms of deterioration in a marine ignition switch include difficulty or inability to turn the contact, positions that do not respond correctly (the engine will not start despite turning the key to the start position), intermittent loss of electrical accessories in the accessory position, or a contact that becomes stuck and does not return to the rest position. Continuous exposure to moisture and the salt-laden environments typical of the marine setting accelerates corrosion of the internal contacts, so it is recommended to inspect this component at each seasonal service interval. Replacing the ignition switch preventively at the first signs of irregular operation avoids being unable to start at sea, where an electrical failure can become an emergency situation.

Mercury / MerCruiser

Equivalent manufacturer references