Sierra RPM Limiter 18-99257 for Mercury/Mariner 2-Stroke Outboards, 1992-2006, Replaces 821889A36, 5800 RPM

The Sierra 18-99257 RPM Limiter is an ignition component for Mercury and Mariner 2-stroke outboards and SportJet engines that require a 5800 RPM operating limit. It installs into the existing ignition circuit to cap engine speed at the factory-specified threshold, protecting the powerhead from over-revving during operation. This is a direct-fit replacement designed to restore the RPM-limiting function on engines covering model years 1992 through 2006.

The RPM limiter is a compact electronic module wired into the outboard's ignition system. When engine speed approaches the 5800 RPM ceiling, it intervenes to prevent the engine from exceeding that limit, which helps guard against mechanical damage from sustained over-revving. It is a straightforward swap for the original factory unit, using the same electrical interface so no rewiring or ECU changes are needed.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99257
• Application: Mercury/Mariner 2-stroke outboards and SportJet engines
• RPM Limit: 5800 RPM
• Weight: 0.3 pounds
• UPC: 808282394196

Fitment

• Mercury/Mariner 2-stroke outboards and SportJet engines requiring a 5800 RPM limit, 1992-2006

Replaces (OEM)

• 821889A36
• 821889A52
• 821889A2
• 821889A4
• 821889A6
• 821889A8
• 821889A12
• 821889A14
• 821889T24
• 821889A48
• 821889A44
• 821889A18
• 821889A24
• 821889A31
• 821889A32

Frequently Asked Questions

What engines does the Sierra 18-99257 RPM Limiter fit? It fits Mercury/Mariner 2-stroke outboards and SportJet engines built to a 5800 RPM operating limit, covering model years 1992 through 2006.

What RPM does this limiter cap the engine at? The Sierra 18-99257 caps engine speed at 5800 RPM, matching the factory limit for the covered Mercury/Mariner 2-stroke and SportJet engines.

Is the Sierra 18-99257 a direct replacement for the factory Mercury part? Yes, it is a direct replacement using the same electrical interface as the original Mercury/Mariner ignition component, so no wiring or ECU modifications are needed.

Which OEM part numbers does part 18-99257 replace? It replaces Mercury/Mariner numbers 821889A36, 821889A52, 821889A2, 821889A4, 821889A6, 821889A8, 821889A12, 821889A14, 821889T24, 821889A48, 821889A44, 821889A18, 821889A24, 821889A31, and 821889A32.

How much does the 18-99257 RPM Limiter weigh? This RPM limiter weighs 0.3 pounds.

Will this part work on a SportJet engine? Yes, the Sierra 18-99257 is built for SportJet engines that require a 5800 RPM limit, in addition to Mercury/Mariner 2-stroke outboards.

Does installing the 18-99257 require any special tools or programming? No special programming is required; the Sierra 18-99257 wires into the existing ignition circuit in place of the original RPM limiter using the stock connections.

What happens if the RPM limiter fails or is left out? Without a functioning RPM limiter like the Sierra 18-99257, the engine loses its 5800 RPM ceiling and can be run past its designed speed limit, increasing the risk of powerhead damage.

Is the 18-99257 compatible with both Mercury and Mariner branded outboards? Yes, part 18-99257 is designed for both Mercury and Mariner 2-stroke outboards sharing the 5800 RPM ignition specification, as well as SportJet engines.

Does this part cover a specific year range? The Sierra 18-99257 is specified for engines within the 1992 to 2006 model range that require a 5800 RPM limit.

What is the UPC for the Sierra 18-99257 RPM Limiter? The UPC for this part is 808282394196.