Sierra 18-5812 Marine Solenoid, Isolated Base, 12 Volt, for OMC Cobra Stern Drive 4.3L-7.5L

The Sierra 18-5812 is a 12 volt marine solenoid built with an isolated base for OMC Cobra Stern Drive applications. It is designed to meet or exceed original equipment quality, giving boat owners a dependable way to restore starting and electrical switching function without sourcing a discontinued original equipment part. The solenoid has a white finish and a machined exterior, and its isolated base construction keeps the electrical circuit separated from the mounting surface, which helps prevent stray grounding issues on stern drive electrical systems.

This solenoid is a direct fit for a range of OMC Cobra Stern Drive engine sizes and model years, making it a straightforward replacement for boaters who need to match their existing setup exactly. Because it is fit specific, buyers should confirm their engine size and model year against the fitment listed below before ordering. The 18-5812 is sized at 6 x 2.5 x 6 inches and weighs 0.62 pounds, keeping it consistent with the compact solenoid form factor expected on stern drive engines.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5812
• Product Type: Marine Solenoid
• Voltage: 12 Volts
• Base Type: Isolated base
• Color: White
• Exterior Finish: Machined
• Product Dimensions: 6 x 2.5 x 6 inches
• Weight: 0.62 pounds
• OEM Cross Reference: OMC 985063, OMC 982187, OMC 581528, 172869, Arco SW268, GLM 72403, Mallory 9-15107

Fitment

• OMC Cobra Stern Drive 4.3L, 1989-90
• OMC Cobra Stern Drive 5.0L, 1986-88
• OMC Cobra Stern Drive 5.7L, 1986-88
• OMC Cobra Stern Drive 5.7L, 1989
• OMC Cobra Stern Drive 7.5L, 1987

Replaces (OEM)

• OMC 985063
• OMC 982187
• OMC 581528
• 172869
• Arco SW268
• GLM 72403
• Mallory 9-15107

Frequently Asked Questions

What is the Sierra 18-5812 used for? The Sierra 18-5812 is a 12 volt marine solenoid used on OMC Cobra Stern Drive engines to handle electrical switching, most commonly in the starting circuit.

Will the 18-5812 fit my OMC Cobra Stern Drive engine? Fitment depends on engine size and model year: the 18-5812 fits the 4.3L (1989-90), 5.0L (1986-88), 5.7L (1986-88 and 1989), and 7.5L (1987) OMC Cobra Stern Drive engines. Because this solenoid is fit specific, confirm your engine size and year before ordering.

Is the Sierra 18-5812 a 12 volt solenoid? Yes, the 18-5812 is a 12 volt solenoid with an isolated base.

What does isolated base mean on this solenoid? An isolated base means the electrical circuit inside the 18-5812 solenoid is separated from the metal mounting base, which helps prevent unwanted grounding through the mounting surface.

What OEM part numbers does the Sierra 18-5812 replace? The 18-5812 replaces OMC 985063, OMC 982187, OMC 581528, and 172869, and is interchangeable with Arco SW268, GLM 72403, and Mallory 9-15107.

What color and finish is the 18-5812 solenoid? This solenoid has a white housing with a machined exterior finish.

What are the dimensions and weight of the 18-5812? The Sierra 18-5812 measures 6 x 2.5 x 6 inches and weighs 0.62 pounds.

Is the Sierra 18-5812 an original equipment part or aftermarket? The 18-5812 is an aftermarket replacement solenoid built to meet or exceed original equipment quality, not an original OMC-branded component.

Does the 18-5812 come with mounting hardware? The dossier for the 18-5812 does not list included mounting hardware; it covers only the solenoid itself.

How is the Sierra 18-5812 different from OMC 985063? Functionally the 18-5812 is a direct cross reference to OMC 985063, providing the same isolated base 12 volt solenoid operation for OMC Cobra Stern Drive engines.