Mercury MerCruiser Quicksilver — Thermostat Housing to Reservoir Gasket — 74830
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Mercury MerCruiser Quicksilver Thermostat Housing to Reservoir Gasket 74830
Mercury MerCruiser Quicksilver 74830 is the thermostat-housing-to-reservoir gasket used in the cooling system on MerCruiser MCM and MIE 470 engines. It installs between the thermostat housing and coolant reservoir to provide the sealing surface at this joint.
Compatible Applications
- MerCruiser MCM 470-series engines
- MerCruiser MIE 470-series engines
- Mercury-built inline-four 470 engine family where the OEM cooling-system diagram specifies 74830
Serial-number fitment: MerCruiser 470 engines were produced in multiple configurations and serial ranges. Confirm the engine model, serial number, and exact diagram location before ordering, particularly if cooling-system components have previously been replaced.
Part Details
- Part number: 74830
- Mercury catalog number: 27-74830
- Brand: Mercury MerCruiser Quicksilver
- Product type: Thermostat-housing-to-reservoir gasket
- System: Engine cooling system
- Quantity: One gasket per applicable assembly
- Condition: New
Key Features
- Genuine OEM replacement gasket
- Seals the joint between the thermostat housing and coolant reservoir
- Diagram-specific fitment for MCM and MIE 470 applications
- Distinct from the thermostat-housing-to-exhaust-manifold gasket
When to Replace This Gasket
Replace gasket 74830 whenever the reservoir is removed from the thermostat housing or if coolant seepage is present at the joint. Do not reuse a gasket that is compressed, torn, hardened, swollen, or damaged during disassembly.
Installation Notes
Clean the thermostat-housing and reservoir mating surfaces before fitting the new gasket. Remove old gasket material without damaging the sealing surfaces, and inspect both components for corrosion, distortion, or pitting. Follow the applicable Mercury service procedure for fastener tightening and cooling-system refill.
Related Part Clarification
Part 480431 or 27-48043 is a different nearby gasket used between the thermostat housing and exhaust manifold. It is not interchangeable with 74830.
Technical FAQ
Where does 74830 install?
It installs between the thermostat housing and coolant reservoir on applicable MerCruiser 470-series engines.
Is this the thermostat-housing-to-exhaust-manifold gasket?
No. That nearby joint uses a different gasket, referenced as 480431 or 27-48043.
How many are required?
Applicable diagrams show one 74830 gasket per assembly.
Parts Desk Insights
Best use case: Resealing the coolant reservoir to the thermostat housing during cooling-system service on a compatible MCM or MIE 470 engine.
Most common mistake: Confusing 74830 with the nearby thermostat-housing-to-exhaust-manifold gasket. The two seals serve different joints.
Fitment guidance: Match the part number and diagram location, then confirm the engine model and serial number before ordering.
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.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.