Mercury Quicksilver Extended Life Coolant/Antifreeze 877770K1 | 1 Gallon Concentrate
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Mercury Quicksilver Extended Life Coolant/Antifreeze 877770K1
Part Number: 877770K1 | Also listed as: 92-877770K1 / 92-877770Q1
Brand: Mercury / Quicksilver
Official Product Type: Extended Life Coolant/Antifreeze — 1 US Gallon Concentrate
System: Engine Cooling (Closed Cooling / Fresh Water Cooling)
A genuine OEM extended-life coolant/antifreeze formulated specifically for Mercury and MerCruiser marine engines. Provides corrosion protection for aluminum, cast iron, copper, and other metals found in marine closed-cooling systems. Mix with distilled water to achieve the desired freeze protection level before use.
Compatible Applications
- MerCruiser closed-cooling (fresh water cooling) systems — all applicable engine families
- Mercury L6 Verado In-Line 6-Cylinder Outboards (closed-cooling equipped)
- Mercury V8 / V10 Verado Outboards (closed-cooling equipped)
- MerCruiser sterndrive engines with factory or aftermarket closed-cooling kits
- Any Mercury or MerCruiser engine requiring an OEM-specified extended-life coolant
Always verify compatibility against your engine's service manual or owner's manual before use. Not all Mercury outboards use a closed-cooling system — confirm your engine is equipped with one before ordering.
Part Details
- Format: Concentrate — must be diluted with distilled water before use
- Volume: 1 US Gallon (3.78 L)
- Type: Extended Life Coolant (ELC) — OAT (Organic Acid Technology) formula
- Color: Yellow/Gold (typical for OAT extended-life formulas)
- System compatibility: Aluminum, cast iron, copper, brass, and rubber components
Service Interval
Mercury recommends replacing extended-life coolant every 5 years or 1,000 hours, whichever comes first. Always inspect the cooling system for leaks, hose condition, and thermostat function at each service interval. Flush the system before refilling with fresh coolant.
Mixing & Usage Notes
- Always mix with distilled water only — tap water introduces minerals that reduce corrosion protection.
- Standard mix ratio: 50/50 concentrate to distilled water for protection to approximately -37°C / -34°F.
- For pre-mixed convenience, see the Quicksilver Extended Life Coolant/Antifreeze – Pre-Diluted 50/50, 1 Gallon.
- Do not mix with other coolant types or brands — flush the system completely before switching formulas.
- After filling, run the engine to operating temperature, check for leaks, and recheck the coolant level once cooled.
Parts Desk Insights
Best use case: This is the correct OEM coolant for MerCruiser closed-cooling systems and Verado engines that specify an extended-life formula. It is the right choice when you want a genuine Mercury product with no compatibility guesswork — particularly for aluminum-heavy engine families where the wrong coolant chemistry can cause accelerated corrosion.
Common mistakes: The most frequent error is ordering the concentrate when the customer actually wants the pre-mixed 50/50 version — or vice versa. Confirm whether the customer needs to mix it themselves or wants a ready-to-use product. A second common mistake is assuming all Mercury outboards have closed-cooling systems; most raw-water-cooled outboards do not use this product at all. Always verify the engine has a closed-cooling system before recommending this coolant.
Related Parts
- Quicksilver Extended Life Coolant/Antifreeze – Pre-Diluted 50/50, 1 Gallon
- Quicksilver Extended Life Coolant/Antifreeze 92-877770Q1 (Case)
- MC-342 Fresh Water Closed Cooling Kit – MerCruiser 3.0L / 3.0LX
- Mercury MerCruiser Coolant Recovery Kit 71587A10
- Mercury Fogging Oil 858081K03 – Storage Protection Spray
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.