Mercury MerCruiser Rear Crankshaft Oil Seal 26-75980 | GM 454 7.4L Reverse Rotation
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Mercury MerCruiser Rear Crankshaft Oil Seal — Part 26-75980
- Part Number: 26-75980 (also referenced as 75980, 75980T, 26-75980T)
- Brand: Mercury / MerCruiser (OEM reference)
- Official Product Type: Gaskets & Seals — Internal Engine
- System: Crankshaft Sealing / Rear Main
- Application: Rear crankshaft / rear bearing-cap oil seal, right-hand / reverse-rotation engines only
- Qty Required: 1 per engine
- OEM Availability: Original Mercury 26-75980 is currently listed as no longer available (NLA) from Mercury. Aftermarket replacements are available for these applications.
What It Does
This rear crankshaft oil seal fits the bearing-cap area at the back of the engine, preventing oil from escaping between the crankshaft and the rear main bearing-cap. 26-75980 is specifically for right-hand / reverse-rotation GM 454 engines — MerCruiser used a different seal for standard left-hand rotation engines of the same displacement. Confirming engine rotation before ordering is essential.
Compatible Applications
Verify fitment by engine serial number and confirm reverse/right-hand rotation before ordering.
- 330 GM 454 V8 — 1977–1981 | Serial range: 4623115 through 6083144
- 330 MIE GM 454 V8 — 1977–1980 | Serial range: 4623115 through 5889913
- 340 MIE with Borg Warner transmission — 1981–1987 | Serial range: 5889914 through 0B788365
- 7.4L MIE with Borg Warner transmission — 1988–1992 | Serial range: 0B788366 through 0D715493
Not sure it fits? Send us your MerCruiser engine serial number and confirm your engine's rotation direction before ordering.
Part Numbers & Cross-References
- 26-75980 — Mercury / MerCruiser OEM part number
- 75980 — Short-form Mercury reference
- 75980T / 26-75980T — Related Mercury-format reference
- FEL17740 / Fel-Pro 17740 — Aftermarket replacement for reverse-rotation applications
Because the original Mercury part is NLA, aftermarket equivalents are the primary service option for these older reverse-rotation engines.
When to Replace
Replace this seal when:
- Engine oil is leaking from the rear crankshaft area
- The seal is hardened, cracked, or damaged on inspection
- Leakage is discovered during flywheel or transmission removal
- The engine is being overhauled or the rear bearing cap is being serviced
Oil appearing between the engine block and transmission can come from multiple sealing points — diagnose the source carefully before replacing parts.
Installation Notes
- Confirm engine rotation is right-hand / reverse before installation — do not substitute the standard-rotation seal
- Verify the engine serial number falls within the ranges above
- Inspect the crankshaft sealing surface for grooves or wear before fitting a new seal
- Clean the bearing-cap and block sealing surfaces thoroughly
- Follow the applicable MerCruiser service procedure for seal orientation and torque specs
- Mercury parts diagrams list 26-75980 separately from the standard-rotation rear seal — confirm the correct diagram position for your engine before installation
Parts Desk Insights
The most common mistake with this seal is ordering a GM 454 rear main seal without confirming engine rotation. Standard and reverse-rotation 454 engines use different seals, and they are not interchangeable. If you're working on a 330 MIE, 340 MIE, or the reverse-rotation 7.4L MIE, this is the correct seal — but always cross-check your serial number against the ranges above. Because the original Mercury part is discontinued, an aftermarket equivalent such as the Fel-Pro 17740 is the typical service solution for these engines.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
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