Quicksilver Water Pump Housing O-Ring 29439 | 1.185 in. ID | Mercury MerCruiser OEM
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Quicksilver OEM Water Pump Housing O-Ring — Part No. 29439 / 25-29439
- Part Number: 29439
- Service Format: 25-29439
- Brand: Quicksilver (Genuine Mercury Marine OEM)
- Type: O-Ring — Water Pump Housing Seal
- Inside Diameter (ID): 1.185 in. / 30.1 mm
- Width (Cross-Section): 0.100 in. / 2.5 mm
- GTIN / UPC: 745061133464
- System: Cooling / Lower Unit — water pump housing and gear housing sealing
What This Part Does
This genuine OEM O-ring seals the water pump housing in compatible Mercury, Mariner, and MerCruiser assemblies. A failed or aged water pump housing O-ring allows cooling water to bypass or leak at the housing joint, which can reduce pump efficiency and lead to overheating. This O-ring should be replaced any time the water pump housing is opened — reusing the old seal is not recommended as it compresses and loses its sealing ability over time.
Compatible Applications
Mercury / Mariner Outboards (confirm by serial number):
- 3.9 HP, 4 HP, 4.5 HP outboards
- 6 HP, 7.5 HP outboards
- 9.8 HP outboards
- 40 HP, 60 HP outboards
- 75 HP, 110 HP outboards
- Selected Mark-series outboard applications
MerCruiser Big-Block Applications (confirm by serial number):
- 454 MAG MPI Horizon
- 7.4L MPI MIE
- 8.2L MIE MPI
- 454 MAG MPI Bravo
- 502 MAG MPI Bravo
Always confirm by exact engine or drive serial number and the current Mercury parts diagram before ordering — 29439 appears across both outboard and MerCruiser gear housing/water pump housing applications.
Aftermarket Cross-References
- Sierra 18-7156 / 18-7156-9
- GLM 81230
- Johnson / Evinrude / OMC 309731
- Volvo Penta 3852537 (related cross-reference in supported applications)
When to Replace
- Any time the water pump housing or gear housing is opened for service
- O-ring is flattened, cut, brittle, swollen, cracked, or missing
- Water pump is leaking at the housing joint
- During routine water pump impeller replacement — replace all housing seals at the same time
Installation Notes
- Clean the O-ring groove and mating surface thoroughly before installing the new seal
- Lightly lubricate the O-ring with the lubricant specified in the Mercury service manual for the assembly
- Seat the O-ring evenly in the groove — avoid twisting, pinching, or rolling during installation
- Confirm the exact groove location in the Mercury parts diagram before fitting
- Do not reuse the old O-ring after removal
Related Products
- Mercury MerCruiser Quicksilver Water Pump Repair Kit 8M0135821
- Mercury Water Pump Gasket 858524 — MerCruiser Alpha One & Outboard
- Mercury MerCruiser Water Pump to Gear Housing Gasket 27-85610
- Mercury MerCruiser Quicksilver Water Pump Cover-to-Face-Plate Gasket 43033
- Marine Gaskets, Seals & O-Rings
- Mercury MerCruiser Gaskets & Seals
Parts Desk Insights
29439 is one of those O-rings that’s worth adding to any water pump service order as a matter of routine — the housing is already apart, the part is inexpensive, and an aged O-ring that weeps at the housing joint will bring the engine back to the bench for repeat work. The broad application range (small outboards through big-block MerCruiser) means it’s important to confirm by serial number and diagram rather than engine family alone. The most common issue is reusing the old O-ring during reassembly: it has already taken a compression set and will not seal with the same reliability as a new part.
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
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
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.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
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For return authorization, please contact our support team before shipping anything back.