Mercury Antifreeze -100°F 1 Gallon | 8M0073203
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Mercury Marine Antifreeze – 1 Gallon | Part 8M0073203
Part Number: 8M0073203
Brand: Mercury Marine / Quicksilver
Official Product Type: Marine Water-System Antifreeze
Container Size: 1 Gallon (3.78 L)
Formula: Non-toxic propylene glycol blend
Temperature Rating: Burst protection to -100°F (-73°C) | Freeze protection approx. -58°F to -63°F (-50°C to -52°C)
What It Does
This is a water-system antifreeze designed for seasonal winterization — not an engine coolant for closed-cooling systems. It displaces water from raw-water cooling passages, livewells, wash-down systems, and onboard plumbing to prevent freeze damage during off-season storage. The blue-green dye lets you visually confirm the antifreeze has circulated fully through the system.
Key Features
- Burst protection to -100°F (-73°C)
- Freeze protection approx. -58°F to -63°F (-50°C to -52°C)
- Non-toxic propylene glycol — safe for raw-water and potable water systems
- Inhibits corrosion of aluminum, copper, brass, and solder
- Compatible with rubber seals, gaskets, and hoses
- Blue-green dye for easy visual confirmation during winterization
- Genuine Mercury Marine / Quicksilver OEM formulation
Compatible Applications
Designed for winterizing raw-water cooling systems, livewells, and onboard plumbing on:
- Mercury Outboards — 2.5HP through 400HP (FourStroke, Pro XS, Verado, SeaPro)
- MerCruiser Sterndrives — 3.0L, 4.3L V6, 5.0L V8, 5.7L V8, 6.2L V8, 7.4L V8, 8.2L V8
- MerCruiser Inboard engines with raw-water cooling
- Livewell and baitwell systems
- Freshwater plumbing and wash-down systems on boats
- Raw-water cooling systems on RVs and marine vessels
System
Raw-water cooling system / water-system winterization. Not for use in closed-cooling (freshwater) engine systems — those require a separate engine coolant. Always follow the manufacturer's winterization procedure for your specific engine model.
Dimensions
1 Gallon jug — approximately 6" W × 6" D × 11" H. Weight: 8.3 lbs (3.78 kg) filled.
Related Parts
Commonly used together during winterization and cooling system service:
- Mercury Quicksilver Outboard Flushing Attachment 12612T2 — flush before winterizing
- FlushMaster Flush Port Quick Connect – Mercury Outboard
- Mercury Water Pump Impeller 19453T — replace impeller at winterization
- Mercury MerCruiser Water Pump Repair Kit 8M0135821
- Mercury MerCruiser Thermostat Kit 807252T5
- Mercury Outboard Thermostat Assembly 120°F – 8M0090819
- Mercury Quicksilver High Performance Gear Lube 858058KC1 — complete winterization service
Service Interval
Use annually at the start of each winterization / lay-up. Replace with fresh antifreeze each season — do not reuse antifreeze from the previous year. Flush the system thoroughly with fresh water before re-commissioning in spring.
Technical FAQ
Can I use this in my closed-cooling system?
No. This product is for raw-water and water-system winterization only. Closed-cooling systems require a separate ethylene or propylene glycol engine coolant rated for your system.
Do I dilute this antifreeze?
Generally used full-strength for winterization. Always follow the specific winterization procedure in your engine's service manual for correct application and volume.
Is it safe if it enters the water?
Yes — the propylene glycol formula is non-toxic and environmentally safer than ethylene glycol antifreeze, making it appropriate for marine use near water.
How do I know it's circulated fully?
The blue-green dye will be visible at the water outlet when the antifreeze has fully displaced water from the system.
Parts Desk Insights
Best use case: Annual winterization of outboard and sterndrive raw-water cooling systems, livewells, and onboard plumbing in climates where temperatures drop below freezing. One gallon is typically sufficient for a single outboard or sterndrive winterization.
Common mistakes:
- Using this in a closed-cooling system — it is not formulated for that application and will not provide the correct protection. Use a dedicated engine coolant instead.
- Skipping the flush step — always flush the system with fresh water before introducing antifreeze to remove salt, debris, and contaminants.
- Reusing last season's antifreeze — inhibitors degrade over time. Use fresh antifreeze each season for reliable protection.
- Not confirming full circulation — watch for the blue-green dye at the outlet before shutting down. If you don't see it, the antifreeze hasn't reached all passages.
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.