Sierra 18-0614 Rear Main Seal, Replaces Mercruiser 845668T, for GM Big Block V8 (Right Handed Dipstick)

The Sierra 18-0614 is a 1-piece rear main seal engineered for GM Big Block V8 marine engines equipped with a right-handed dipstick. Installed at the rear of the crankshaft where it meets the flywheel housing, this seal keeps engine oil contained and prevents leaks at one of the most common failure points on inboard and sterndrive engines. Its 1-piece design simplifies installation compared to older 2-piece seal setups, reducing the number of parting lines that can become a leak path over time.

Sierra builds this seal to fit as a direct equivalent for the Mercruiser rear main seals it replaces, so it installs using the same engine preparation and hardware as the original part. It is intended for use during rear main seal replacement, engine rebuilds, or any repair where oil is leaking from the rear of the crankshaft on a GM Big Block V8 marine engine with a right-handed dipstick configuration.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-0614
• Product Type: Rear Main Seal
• Seal Design: 1-piece
• Application: GM Big Block V8 (Right Handed Dipstick)
• Weight: 13.63 pounds
• OEM Cross Reference: 845668T, 850458, 811549

Fitment

• Mercruiser GM Big Block V8 engines with right-handed dipstick configuration

Replaces (OEM)

• 845668T
• 850458
• 811549

Frequently Asked Questions

What engines does the Sierra 18-0614 rear main seal fit? The Sierra 18-0614 is designed for GM Big Block V8 marine engines with a right-handed dipstick configuration.

Is the Sierra 18-0614 a 1-piece or 2-piece rear main seal? It is a 1-piece rear main seal, which uses a single continuous seal rather than two separate seal halves.

What OEM part numbers does the Sierra 18-0614 replace? It replaces Mercruiser rear main seal part numbers 845668T, 850458, and 811549.

Will the Sierra 18-0614 work on a GM Big Block V8 with a left-handed dipstick? No. The 18-0614 is built for the right-handed dipstick configuration; GM Big Block V8 engines with a different dipstick placement require a different Sierra rear main seal.

How much does the Sierra 18-0614 rear main seal weigh? The Sierra 18-0614 has a shipping weight of 13.63 pounds.

When would I need to replace this rear main seal? Replacement is needed when oil is leaking from the rear of the crankshaft near the flywheel housing on a GM Big Block V8 marine engine, or during an engine rebuild.

Is the Sierra 18-0614 an OEM part or an aftermarket replacement? The 18-0614 is a Sierra-manufactured replacement seal designed to cross-reference directly to Mercruiser OEM numbers 845668T, 850458, and 811549.

Does installing a 1-piece rear main seal require different tools than a 2-piece seal? The Sierra 18-0614's 1-piece design installs using standard rear main seal installation procedures for GM Big Block V8 engines; no special tools beyond standard seal installation are implied by its design.

What brand makes the 18-0614 rear main seal? The 18-0614 is manufactured by Sierra.

Can I use the Sierra 18-0614 to cross-reference a Mercruiser 850458 seal? Yes, Mercruiser 850458 is one of the OEM numbers the Sierra 18-0614 directly replaces.