Sierra Shift Assist Module & Harness 18-5890-1, Replaces OMC 987740/985902, Fits OMC 2.3, 3.0, 4.3 (1986-90) & 2.5 (1986) Sterndrive

The Sierra 18-5890-1 Shift Assist Module & Harness is a direct-fit replacement electrical module used to restore smooth, reliable shift operation on OMC sterndrive engines. The kit includes the shift assist module along with its wiring harness, allowing for a straightforward swap in place of the original equipment module without splicing in a separate harness. The housing is constructed of aluminum with a white finish, matching the original module's build for durable, long-term service in the marine engine compartment.

This module is engineered to meet or exceed the performance of the original equipment part it replaces, making it a dependable choice for engine owners who need to restore correct shift function. It is built for OMC sterndrive engines in the 2.3, 3.0, and 4.3 displacement range (1986-90) as well as the 2.5 displacement (1986), covering the shift assist electronics for these specific engine years.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5890-1
• Product Name: Shift Assist Module & Harness
• Replaces (OEM): 987740, 985902
• Fitment: OMC 2.3, 3.0, 4.3 (1986-90) & 2.5 (1986)
• Material: Aluminum
• Color: White
• Item Dimensions: 6 x 1.5 x 6 inches
• Weight: 0.49 pounds
• UPC: 808282392413

Fitment

• OMC 2.3, 3.0, 4.3 sterndrive engines (1986-90)
• OMC 2.5 sterndrive engine (1986)

Replaces (OEM)

• 987740
• 985902

Frequently Asked Questions

What does the Sierra 18-5890-1 replace? The Sierra 18-5890-1 shift assist module and harness replaces OMC part numbers 987740 and 985902.

Which engines does this shift assist module fit? It fits OMC sterndrive engines in the 2.3, 3.0, and 4.3 range built in 1986-90, as well as the 2.5 engine built in 1986.

Does the 18-5890-1 include the wiring harness? Yes, the kit includes both the shift assist module and its matching wiring harness for a complete swap.

What material is the module housing made of? The Sierra 18-5890-1 module has an aluminum housing finished in white.

How much does the Sierra 18-5890-1 weigh? The Sierra 18-5890-1 shift assist module and harness weighs 0.49 pounds.

What are the dimensions of the shift assist module? The module measures 6 x 1.5 x 6 inches.

Is this a genuine Sierra part or an aftermarket copy? It is a genuine Sierra part, manufactured to meet or exceed the performance of the original OMC shift assist module it replaces.

Will part number 987739 or the Ford 5.0/5.8 sterndrive shift module also work in place of this one? No, that is a different part number and engine application; the Sierra 18-5890-1 is specific to OMC 2.3, 3.0, 4.3 (1986-90) and 2.5 (1986) sterndrive engines.

What is the UPC for the Sierra 18-5890-1? The UPC for the Sierra Shift Assist Module & Harness (18-5890-1) is 808282392413.

Can this module be installed without additional wiring modifications? Since the 18-5890-1 kit includes the correct matching harness, it is designed to install in place of the original module and harness without needing to splice in a separate harness.

Does the Sierra 18-5890-1 come as a complete kit or just the module? It is sold as a complete kit consisting of the shift assist module and its wiring harness.