Mercury Power Tune Internal Engine Cleaner – 858080K03 | 12 oz Spray

Mercury Power Tune Internal Engine Cleaner – 858080K03

Restore lost power and smooth out rough-running performance with Mercury Power Tune, a genuine OEM internal engine cleaner formulated to break down and remove carbon, gum, and varnish deposits from combustion chambers, intake valves, and fuel passages. These deposits build up gradually from normal use, low-temperature operation, and certain fuel blends — and they rob engines of power and efficiency long before most owners notice.

Compatible Applications

• All Mercury and MerCruiser 2-stroke gasoline engines (carbureted and fuel-injected)
• All Mercury and MerCruiser 4-stroke gasoline engines (carbureted and fuel-injected)
• Catalyzed (catalyst-equipped) engines — safe for use with catalytic converters
• Not for use in diesel engines

Part Details

• OEM Part Number: 858080K03
• Mercury Reference Number: 92-858080K03
• Brand: Mercury / Quicksilver
• Product Type: Internal engine cleaner — aerosol spray
• Container Size: 12 oz (340 g) aerosol spray can
• System: Combustion chamber, intake, and fuel/air passages
• Condition: New OEM

What It Does

• Dissolves carbon, gum, and varnish deposits from combustion chambers and intake passages
• Helps restore fuel and air flow to factory specification
• Improves throttle response and smooths rough idle caused by deposit buildup
• Safe for catalyzed engines — will not damage oxygen sensors or catalytic converters
• Works on both 2-stroke and 4-stroke gasoline engines

Service Interval

Use as needed when the engine shows signs of power loss, rough idle, or hesitation caused by combustion-chamber deposits. Mercury also recommends it as part of seasonal maintenance when engines have seen extended low-load or low-temperature operation, or when fuel quality has been inconsistent.

How to Use

Apply as directed on the label. Typically sprayed into the air intake or carburetor throat with the engine running, allowing the cleaner to pass through the combustion chambers. Follow Mercury’s application instructions for the specific engine type. Do not use in diesel engines.

Technical FAQ

• Is this safe for fuel-injected engines? Yes — Mercury specifies it for both carbureted and EFI gasoline engines.
• Can I use this on a catalyzed engine? Yes — 858080K03 is formulated to be safe for catalyst-equipped engines.
• Will this clean the fuel injectors? Power Tune targets combustion-chamber and intake deposits. For fuel injector cleaning, a dedicated fuel system treatment is more appropriate.
• How often should I use it? As needed based on symptoms, or as part of seasonal service. It is not a substitute for regular tune-up maintenance.
• Is 858080K03 the same as 92-858080K03? Yes — 92- is Mercury’s internal prefix for chemical products. Both numbers refer to the same item.

Related Parts

• Mercury 40–60 HP FourStroke EFI 100-Hour Maintenance Kit – 8M0232733
• Mercury Engine Maintenance Parts Collection

Parts Desk Insights

Power Tune is the right call when an engine has been running rough, losing power, or idling poorly and the tune-up parts (spark plugs, filters) are already fresh. It’s particularly effective on engines that have seen a lot of idling, cool-weather running, or ethanol-blended fuel — all of which accelerate deposit buildup in the combustion chamber. The most common mistake is using it as a substitute for a proper tune-up: Power Tune cleans deposits, but it won’t fix worn spark plugs, a dirty fuel filter, or a failing ignition component. Use it alongside — not instead of — regular maintenance. Also note: this is an internal cleaner, not a fuel system additive — it goes through the air intake, not the fuel tank.