Sierra 18-6420 Outboard Starter, Replaces Yamaha 6N7-81800-10-00, Fits 115-250 HP (9 Tooth)

The Sierra 18-6420 is a marine-grade outboard starter engineered as a direct replacement for Yamaha outboard motors in the 115-250 HP range using a 9 tooth drive configuration. Built to meet SAE J1171 and ISO 8846 marine electrical standards, this starter is designed to withstand the vibration, moisture, and thermal cycling that shorten the life of automotive-grade starters when used in a marine environment.

Inside the housing, high quality magnets and field coils are matched to deliver strong starting torque for cranking larger displacement outboard powerheads, while double sealed housings and durable brushes are used to extend service life in a wet, corrosive environment. The starter directly replaces Yamaha part number 6N7-81800-10-00, so it drops in without modification to the mounting, drive gear, or electrical connections on applicable outboards.

As a Sierra part, the 18-6420 is covered under Sierra's Customer Satisfaction Warranty, which warrants the product against defects in workmanship and materials for the useful life of the product. This starter is intended for outboard owners and marine technicians replacing a failed or worn starter motor rather than for new-engine assembly.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-6420
• Product Type: Outboard Starter
• Drive Tooth Count: 9 tooth
• Fitment: 115-250 HP outboards
• Standards Met: SAE J1171, ISO 8846
• Weight: 3.12 pounds
• UPC: 808282137755

Fitment

• 115-250 HP outboards (9 tooth drive)

Replaces (OEM)

• 6N7-81800-10-00

Frequently Asked Questions

What does the Sierra 18-6420 starter fit? The Sierra 18-6420 fits outboards in the 115-250 HP range that use a 9 tooth drive starter.

What OEM starter does the 18-6420 replace? It replaces Yamaha starter part number 6N7-81800-10-00, so it installs as a direct swap on applicable 115-250 HP outboards.

How many teeth does the drive gear have? The drive gear on the Sierra 18-6420 has 9 teeth, matching the OEM 6N7-81800-10-00 starter it replaces.

Is this a genuine Yamaha part or an aftermarket replacement? The 18-6420 is a Sierra-brand aftermarket starter, not a genuine Yamaha part, built to replace Yamaha 6N7-81800-10-00 on 115-250 HP outboards.

How much does the 18-6420 starter weigh? This starter weighs 3.12 pounds.

What marine standards does this starter meet? Sierra builds the 18-6420 to meet SAE J1171 and ISO 8846 marine electrical standards, which govern ignition protection and safety for marine engine components.

What makes this starter suited for marine use versus an automotive starter? Double sealed housings and marine-grade magnets, field coils, and brushes protect the 18-6420 from the moisture and vibration exposure that automotive starters aren't built to handle in an outboard application.

Does the 18-6420 come with a warranty? Yes, the Sierra 18-6420 is covered under Sierra's Customer Satisfaction Warranty against defects in workmanship and materials for the useful life of the product.

Will the 18-6420 bolt directly onto my outboard without modification? Since it replaces Yamaha 6N7-81800-10-00 directly, the 18-6420 is designed to mount and wire in place without modification on 115-250 HP outboards using that starter.

What is included when I order the 18-6420? The order includes one Sierra 18-6420 outboard starter motor; no separate mounting hardware or wiring harness is included.

Can the 18-6420 be used on smaller horsepower Yamaha outboards? No, the 18-6420 is built for the 115-250 HP range with a 9 tooth drive and is not the correct starter for smaller Yamaha outboards outside that range.