Sierra 18-5620 Mercury Mariner Outboard Starter Motor

The Sierra 18-5620 is a replacement outboard starter motor engineered for Mercury and Mariner high-horsepower outboard engines. Built to meet or exceed OEM specifications, this 12-volt PMDD (Permanent Magnet Direct Drive) starter features an 8-tooth drive gear with counter-clockwise (CCW) rotation, designed to deliver reliable cranking performance in demanding marine conditions.

Sierra's 18-5620 starter incorporates a marine-grade design with strategically placed seals to minimize water intrusion and prevent moisture accumulation — helping to extend service life in the harsh saltwater and freshwater environments where these engines operate. The updated solenoid design and high-quality field coils provide strong, consistent starting torque, even with a partially discharged battery.

Key Features:

• 12-volt PMDD design with 8-tooth drive gear
• Counter-clockwise (CCW) rotation
• Enhanced sealing to resist water intrusion and moisture accumulation
• Improved solenoid with superior connection between solenoid and commutator brushes
• Updated planetary gear and clutch gear spring for maximized lifespan
• Corrosion-resistant exterior coating to maintain appearance and durability
• Meets or exceeds OEM specifications
• Backed by Sierra's industry-leading customer satisfaction warranty

Replaces OEM Part Numbers:

• Mercury Marine: 50-818445, 50-818445-2, 50-818445-3, 50-818445-5
• Arco: 5395
• Mallory: 9-15028
• United Technologies: 5275640-M030SM, 5672740-M030SM, SM52756, SM56727

Sierra has been a trusted name in marine engine and drive parts for over 50 years, offering high-quality aftermarket components engineered to withstand today's high-horsepower engine demands.