Sierra 18-5408 Distributor Rotor for GM Module in Cap V-6 Distributors, Replaces Mercruiser 850485

The Sierra 18-5408 Rotor is a distributor rotor built for New GM Style "Module in Cap" distributors used in V-6 applications. It is designed to work as a matched pair with the 18-5354 distributor cap, forming the ignition rotor/cap combination that directs spark to the correct cylinder in sequence as the distributor shaft turns. The rotor is constructed of alloy steel with a machined finish for a precise, reliable fit inside the distributor cap and consistent electrical contact against the cap's terminals.

This part is intended as a direct service replacement for worn or pitted rotors on GM V-6 marine engines equipped with module-in-cap distributor ignition systems. A worn rotor can cause misfires, hard starting, and rough idle, so replacing it along with the distributor cap during a routine tune-up helps keep ignition timing accurate across all cylinders. The Sierra 18-5408 is manufactured to meet or exceed the performance of the original equipment rotor it replaces and cross-references to common Mercruiser, OMC, Volvo Penta, GLM, and Mallory part numbers used on the same GM V-6 module-in-cap distributor platform.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-5408
• Material: Alloy Steel
• Exterior Finish: Machined
• Fitment: New GM Style "Module in Cap" Distributors, V-6 Applications
• Companion Distributor Cap: 18-5354
• Weight: 0.03 pounds
• Quantity: 1 rotor
• OEM Cross Reference: GLM 71110, Mallory 9-29221, Mercruiser 850485, 898253012, 850485-1, 8M0062084, 804424, OMC 3854311, Volvo Penta 3854311-2

Fitment

• New GM Style "Module in Cap" Distributors, V-6 Applications
• Use with 18-5354 distributor cap

Replaces (OEM)

• GLM 71110
• Mallory 9-29221
• Mercruiser 850485
• 898253012
• 850485-1
• 8M0062084
• 804424
• OMC 3854311
• Volvo Penta 3854311-2

Frequently Asked Questions

What does the Sierra 18-5408 rotor fit? The Sierra 18-5408 is built for New GM Style "Module in Cap" distributors used in V-6 applications.

Which distributor cap should I use with this rotor? Pair the Sierra 18-5408 rotor with the 18-5354 distributor cap for a correct module-in-cap V-6 ignition setup.

Is the Sierra 18-5408 the same as a Mercruiser 850485 rotor? Yes, the Sierra 18-5408 cross-references to Mercruiser part numbers 850485 and 850485-1, along with 898253012 and 8M0062084, for the same GM module-in-cap V-6 distributor.

Does this rotor cross-reference to OMC or Volvo Penta numbers? Yes, the Sierra 18-5408 replaces OMC 3854311 and Volvo Penta 3854311-2, in addition to GLM 71110 and Mallory 9-29221.

What material is the Sierra 18-5408 rotor made from? It is made of alloy steel with a machined finish for accurate fit and reliable electrical contact inside the distributor cap.

How much does the 18-5408 rotor weigh? The Sierra 18-5408 rotor weighs 0.03 pounds.

How many rotors come in a package? Each package of the Sierra 18-5408 contains 1 rotor.

Is the Sierra 18-5408 genuine OEM or aftermarket? The Sierra 18-5408 is a Sierra-brand aftermarket replacement part manufactured to meet or exceed the performance of the original equipment rotor it replaces.

Will this rotor work with a V-8 module-in-cap distributor? No, the 18-5408 is designed for V-6 module-in-cap distributor applications; V-8 module-in-cap setups use a different rotor.

When should I replace the distributor rotor? A worn or pitted rotor like the 18-5408 should be replaced when experiencing misfires, hard starting, or rough idle, typically alongside the 18-5354 distributor cap during a tune-up.

Does the 18-5408 rotor include the distributor cap? No, the Sierra 18-5408 is the rotor only; the matching 18-5354 distributor cap is a separate part.