Mercury - Water Distributor Thermostat Housing Gasket - 27-475901
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The Mercury MerCruiser Quicksilver 27-475901 Gasket is an OEM cooling-system sealing gasket used on select Mercury MerCruiser sterndrive engines. It seals the water distributor, thermostat cover, or related cooling-housing joint to help keep raw-water or closed-loop cooling flow contained and routed correctly through the engine. This gasket replaces the earlier Mercury part number 27-47590 and is commonly serviced during thermostat housing, water distribution block, or cooling-system repair work.
Key Features
- Mercury / Quicksilver part number: 27-475901
- Superseded Mercury number: 27-47590
- Product type: Cooling-system housing gasket
- Application location: Water distributor / thermostat housing area
- Primary function: Seals cooling-water passage joints against leakage
- System: Raw-water or closed-cooling circuit, depending on engine configuration
- Service use: Thermostat service, water distributor repair, cooling-housing reseal, and leak repair
- OEM status: Genuine Mercury MerCruiser / Quicksilver replacement gasket
Engine Compatibility
This gasket is commonly associated with select legacy Mercury MerCruiser GM-based inline gasoline engines where the parts diagram calls for 27-475901, including applications in the following engine families:
- MerCruiser 120 HP / 2.5L inline 4-cylinder
- MerCruiser 140 HP / 3.0L / 3.0LX inline 4-cylinder
- MerCruiser 160 HP / 165 HP / 200 HP GM inline 6-cylinder applications
- GM 250 CID and 292 CID marine inline 6-cylinder platforms where specified
- Select early Renault 90 sterndrive applications where specified by Mercury diagram
Fitment must be confirmed by engine serial number, model designation, cooling-housing layout, and Mercury parts diagram.
Serial Number Fitment Notice
Mercury cooling-system gaskets are diagram-specific. Confirm the engine serial number and cooling-system parts breakdown before ordering. Similar MerCruiser engines can use different thermostat housings, water distribution blocks, covers, and gasket shapes depending on model year, cooling configuration, and service history.
Do not select this gasket by horsepower or displacement alone. Match it to the exact Mercury diagram callout for 27-475901 or the superseded number 27-47590.
When This Part Needs Replacement
Replace this gasket whenever the thermostat housing, water distributor, or related cooling cover is removed. It should also be replaced if there are signs of water leakage, salt residue, coolant staining, rust trails, corrosion around the housing joint, overheating related to cooling-water loss, or seepage after thermostat service.
A used cooling-system gasket should not be reused after disassembly, as compression set, heat cycling, corrosion, and old gasket residue can prevent it from sealing properly again.
Installation Notes
Clean both mating surfaces before installing the new gasket. Remove old gasket material carefully without gouging aluminum, cast iron, or bronze sealing faces. Inspect the thermostat housing, water distributor, fasteners, hose fittings, thermostat, springs, seals, and nearby cooling passages while the housing is apart.
Follow the Mercury MerCruiser service manual for gasket placement, fastener tightening sequence, torque specification, and sealant requirements. Do not use sealant unless the service procedure calls for it. After reassembly, run the engine to operating temperature and check the housing joint for leaks.
Alternate/Superseded Part Numbers
- Current Mercury / Quicksilver number: 27-475901
- Superseded Mercury number: 27-47590
- Common description: Water Distributor / Thermostat Housing Gasket
- Application reference: Select MerCruiser inline 4-cylinder and inline 6-cylinder cooling-system housings
Parts Desk Insight
This gasket is small, but the cooling-housing match matters. The safest way to identify it is by Mercury serial number and diagram location, not by engine size alone. If the thermostat housing or water distributor is already apart, replace the gasket during reassembly to avoid repeat cooling-water leaks.
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Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
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