Sierra 18-5851 Shrouded Relay, Replaces 865202T 807057T 807057, Mercury/Mariner Outboard

The Sierra 18-5851 is a shrouded relay engineered as a direct replacement for Mercury/Mariner outboard engine electrical systems. The protective shroud housing shields the internal contacts and terminals from moisture, salt spray, and engine bay debris, helping the relay hold up in the harsh marine environment where unshielded automotive-style relays tend to corrode and fail prematurely. This relay is used in Mercury/Mariner outboard applications to switch higher-current circuits, such as trim or starting systems, using a lower-current control signal, protecting the primary switch or control wiring from load current.

Sierra manufactures this relay to meet or exceed the performance of the original equipment part it replaces, and it is built to the same form, fit, and function as the OEM units carrying part numbers 865202T, 807057T, and 807057. As a direct cross-reference replacement, installation follows the same mounting and wiring configuration as the original relay, with no modification required. Sierra backs this part with its Industry Leading Customer Satisfaction Warranty, covering defects in workmanship and materials for the useful life of the product.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5851
• Product Name: Relay, Shrouded
• Weight: 0.6 pounds
• UPC: 808282292539
• Application: Mercury/Mariner outboard engines

Fitment

• Mercury/Mariner outboard engine applications

Replaces (OEM)

• 865202T
• 807057T
• 807057

Frequently Asked Questions

What does the Sierra 18-5851 relay replace? It replaces Mercury/Mariner part numbers 865202T, 807057T, and 807057, making the Sierra 18-5851 a direct cross-reference for any of those three OEM numbers.

Is the 18-5851 a direct OEM replacement or will it need modification? The Sierra 18-5851 shrouded relay is a direct replacement for the Mercury/Mariner 865202T, 807057T, and 807057 relays, designed to match the original mounting and wiring so no modification is needed.

What engines does the 18-5851 relay fit? This shrouded relay is used on Mercury/Mariner outboard engine applications that originally used the 865202T, 807057T, or 807057 relay.

How much does the Sierra 18-5851 relay weigh? The Sierra 18-5851 shrouded relay weighs 0.6 pounds.

What is the purpose of the shroud on this relay? The shroud housing on the Sierra 18-5851 covers the relay's internal contacts and terminals, helping protect them from moisture and salt exposure in a marine engine compartment.

Is the Sierra 18-5851 covered by a warranty? Yes, the Sierra 18-5851 relay is covered under Sierra's Industry Leading Customer Satisfaction Warranty, which covers defects in workmanship and materials for the useful life of the product.

What is included when I order the 18-5851? Ordering the Sierra 18-5851 includes one shrouded relay, ready to install in place of the Mercury/Mariner 865202T, 807057T, or 807057 unit.

Does the 18-5851 use the same UPC across sellers? The Sierra 18-5851 shrouded relay carries UPC 808282292539, which can be used to confirm you are ordering the correct genuine Sierra part.

Can I use the 18-5851 relay for non-Mercury applications? The Sierra 18-5851 is specified for Mercury/Mariner outboard applications that used the 865202T, 807057T, or 807057 relay; compatibility outside those applications is not specified.

Why choose the genuine Sierra 18-5851 over a generic relay? The Sierra 18-5851 is engineered to meet or exceed the original equipment part it replaces and includes Sierra's Customer Satisfaction Warranty, unlike unbranded generic relays without that same coverage.