Mercury MerCruiser Quicksilver Heat Exchanger End Cover Gasket 65128 | 27-65128
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Mercury / Quicksilver OEM Heat Exchanger End Cover Gasket — Part No. 65128 / 27-65128
| Part Number | 65128 / 27-65128 |
|---|---|
| Brand | Mercury Marine / Quicksilver |
| Product Type | Heat Exchanger End Cover Gasket |
| System | Closed / Fresh-Water Cooling |
| Used With | Heat exchanger end cover 66221 |
| Quantity Required | Varies by exchanger design — confirm in cooling-system diagram |
| Sold As | Individually |
| UPC / GTIN | 745061167346 |
About This Part
The 65128 / 27-65128 is a genuine Mercury Marine / Quicksilver OEM gasket that seals the removable end cover on the heat-exchanger tank in selected MerCruiser closed-cooling systems. It installs between the heat exchanger assembly and end cover 66221, preventing coolant or seawater from leaking at the end-cap joint. Mercury parts diagrams position 65128 directly at this interface, and depending on the heat-exchanger configuration, either one or two gaskets may be required — verify the quantity in the applicable cooling-system schematic before ordering.
The fitment of this gasket is determined by the heat-exchanger assembly design, not simply engine displacement. Engines with the same displacement but different cooling-kit configurations may use different gaskets. Always confirm by engine serial number and the applicable closed-cooling schematic.
Compatible Applications
Confirm the engine serial number, closed-cooling kit, and heat-exchanger assembly before ordering. Documented applications include:
- MerCruiser 3.0L / 181 CID inline-4 with applicable closed-cooling package
- MerCruiser 5.7L V8 inboard with applicable heat-exchanger assembly
- MerCruiser Marine 888 / 215 / 225 fresh-water cooling packages
- Other MerCruiser engines equipped with the applicable Mercury heat-exchanger assemblies using end cover 66221
When to Replace
- Any time the heat-exchanger end cover is removed — this gasket should not be reused after compression
- Coolant or seawater leaking around the heat-exchanger end cap
- Gasket is flattened, torn, swollen, brittle, or visibly deteriorated
- Heat exchanger is being cleaned, flushed, or inspected for scale buildup
- End cover or related cooling-system hardware is being replaced
- Closed-cooling system service requiring end-cover removal
Installation Notes
- Verify the quantity required for your heat-exchanger configuration in the Mercury cooling-system diagram — some designs use two 65128 gaskets
- Clean the heat-exchanger tank and end-cover sealing surfaces thoroughly before fitting the new gasket
- Inspect end cover 66221 for corrosion, distortion, or thread damage — replace if sealing surface is compromised
- Check the heat-exchanger tank sealing surface for corrosion pitting around the end-cap bore
- Where applicable, inspect the 75451 fiber washer and 32802 / 328022 brass pipe plug and replace as needed
- Install the new gasket without folding, pinching, or twisting it
- Reassemble and torque the end-cover fastener per the Mercury service manual
- Refill the closed-cooling system and pressure-check for leaks before returning to service
Related Components
Mercury parts diagrams associate the following components with this gasket in closed-cooling heat-exchanger assemblies:
- 66221 — heat exchanger end cover (the mating part this gasket seals)
- 75451 — fiber washer (applicable exchanger configurations)
- 32802 / 328022 — brass pipe plug (applicable exchanger configurations)
- 8M0157284 — current heat exchanger assembly, replacing earlier 61086A7 in selected applications
Parts Desk Insights
This is not a general engine gasket — it is specifically the heat-exchanger end-cover sealing gasket for selected MerCruiser closed-cooling systems. The most reliable way to confirm fitment is to pull the heat-exchanger or cooling-kit diagram for your engine serial number and match by the exchanger assembly number, not just displacement. The quantity needed (one or two) also varies by exchanger design, so check the diagram for that detail before ordering. End-cover leaks on heat exchangers are often slow to show up and easy to overlook — if you’re already removing the end cover for cleaning or inspection, always replace this gasket rather than attempting to reuse it, as a previously compressed gasket rarely reseals reliably.
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.