Best Fuel Injector Cleaner For Outboard Motor: 10 Options Compared

#1 · Best Overall

1. Mercury Quickleen Cleaner

• Size: RM

Best for: Seasonal carbon deposit cleanup.

Why it ranks #1: Mercury Marine makes it for watercraft; it cleans injector carbon and other deposits, with a clear seasonal dose of 1 ounce per 5 gallons.

Mercury Quickleen names a wide range of carbon-prone engine parts, including injectors, carburetors, intake valves, spark plugs, piston crowns, and cylinder heads. Its one-ounce-per-five-gallons direction supports occasional in-season use, giving outboard owners a defined mixing dose for routine fuel-system cleaning and deposit control.

The listed dose of one ounce for five gallons makes measuring an occasional treatment straightforward during the boating season. Quickleen targets deposits across both fuel-system and combustion-related parts, including injectors, carburetors, valves, plugs, crowns, and heads, so its stated cleaning scope extends beyond injectors alone. Mercury says it helps prevent engine knocking and piston seize-up. It does not contain fuel stabilizers, so seasonal cleaning and fuel storage protection are separate tasks.

Skip it if you want cleaning at every fill-up or a treatment that also stabilizes fuel; Quicksilver Quickleen is listed for every-tank use, while Quickleen requires separate stabilization.

A good fit for outboard owners seeking a Mercury-made cleaner for occasional in-season use with an explicit mixing ratio. Keep in mind that it is not a fuel stabilizer, so storage preparation calls for a separate product.

Listed on Amazon as: Mercury 8M0047931 Quickleen Engine & Fuel System Cleaner, 12 oz

#2 · Best Corrosion Protection

2. STA-BIL 360 Marine Treatment

• Volume: 139 cubic in
• Weight: 1.9 lb
• Size: 1 Count (Pack of 1)

Best for: In-season marine fuel care.

Why it ranks #2: Its marine formula uses PEA to clean injectors, lines, and pumps, remove water, gum, and varnish, and protect against corrosion.

STA-BIL 360 Marine uses PEA additives to clean the entire fuel system, including injectors, lines, and fuel pumps. Its listed marine focus also includes water, gum, and varnish removal plus corrosion protection, suiting boat owners who want cleaning and fuel-system protection during the season.

The PEA formula is stated to clean injectors, lines, and fuel pumps, while removing water, gum, and varnish; that broad coverage can make one treatment relevant to several fuel-system maintenance concerns. Corrosion protection is specifically included for internal fuel-system parts, an important listed function for marine use. The bottle directions support measuring small quantities with its long-neck cap and larger quantities from the bottle markings. The stated dose is one ounce per up to ten gallons.

Skip it if you need a cleaner that specifies every-fill-up use and a one-ounce-per-five-gallons dose; Quicksilver Quickleen lists both.

Choose it for marine in-season maintenance when cleaning multiple fuel-system parts and corrosion protection are priorities. Its stated dosing is one ounce per up to ten gallons, so use that rate when planning treatment quantities.

Listed on Amazon as: STA-BIL 360 Marine Fuel System Treatment, 32 oz

#3 · Largest Cleaner Bottle

3. Quicksilver Quickleen Cleaner

• Volume: 32 fluid oz
• Size: 32 Fl Oz (Pack of 1)

Best for: Frequent fill-up treatment.

Why it ranks #3: The 32-fluid-ounce bottle treats injectors and other gasoline-engine parts; it can be used at every fill-up at 1 ounce per 5 gallons.

Quicksilver Quickleen can be used at every fuel-tank fill-up, with one ounce treating five gallons of gasoline. That combination suits boaters who prefer a repeatable dose as part of refueling, while its compatibility with all grades of gasoline and ethanol-blend fuel broadens the fuel types covered by the listing.

The one-ounce-to-five-gallons guidance gives owners a practical measure to scale to a tank fill, and the stated every-fill-up use supports a recurring maintenance routine. Its cleaning targets include injectors and carburetors as well as intake valves, spark plugs, piston crowns, and cylinder heads. Quicksilver also says it helps prevent knocking and piston seize-up. The 32-fluid-ounce bottle provides more product than a single small-dose container, but the listing does not describe storage stabilization.

Skip it if you need a cleaner that explicitly protects stored fuel; Sea Foam Marine PRO lists fuel stabilization alongside marine-system treatment.

Choose this for a gasoline outboard owner who wants a measured cleaner dose at each fill-up and broad fuel compatibility. For storage protection, pair the routine with a product specifically listing fuel stabilization.

Listed on Amazon as: Quicksilver Quickleen Engine and Fuel System Cleaner

#4 · Best 2- or 4-Cycle Fit

4. Johnson Evinrude Cleaner

• Weight: 2 lb

Best for: Johnson Evinrude carbon cleanup.

Why it ranks #4: This factory-original cleaner is listed for 2- and 4-cycle engines and gives separate 16-ounce treatment rates for cleaning and maintenance.

Johnson Evinrude Fuel Systems Cleaner states specific treatment rates for carbon-related injector or carburetor problems: 16 ounces for 36 gallons when addressing malfunction, or 72 gallons for maintenance. It is listed for two- and four-cycle engines, making its guidance relevant across those engine types.

The two treatment rates distinguish corrective use from upkeep: one 16-ounce quantity treats 36 gallons when deposits are causing injector or carburetor malfunction, while the maintenance rate covers 72 gallons. That gives owners a clear basis for choosing a dose according to the stated purpose. The product is identified for two- and four-cycle engines, but it is not for diesel systems. The listing also warns against adding it to lit or burning devices.

Skip it if you run a diesel engine; this cleaner is explicitly excluded, while the listed Sea Foam IC5 is for gasoline fuel-injected engines.

Consider it for a Johnson Evinrude owner treating carbon-related injector or carburetor issues in a two- or four-cycle engine. Follow the stated use rate and keep it away from diesel systems and lit devices.

Listed on Amazon as: Johnson Evinrude Fuel Systems Cleaner 12-oz- 2 or 4 Cycle

#5

5. Sea Foam Marine PRO

• Weight: 4.45 lb

Best for: Marine fuel and storage care.

Why it ranks #5: This marine treatment works through injectors and carburetors, addresses fuel residues and deposits, and also helps stabilize stored fuel.

Sea Foam Marine PRO combines marine fuel-system cleaning with fuel stabilization for boats, jet skis, and other marine engines. It works through injectors and carburetors and is listed for removing residues from fuel passageways, intake valves, pistons, and chamber areas, making its scope broader than injector-only cleaning.

The cleaner's reach across injectors, carburetors, fuel passageways, valves, pistons, and chamber areas suits owners seeking treatment across several marine-engine areas. Its fuel-stabilizer role addresses stored fuel by helping it resist evaporation, preserve ignition vapors, and prevent gum and varnish. Combining those functions can simplify maintenance planning when a boat needs both system cleaning and storage preparation. The product is supplied as a three-pack of 20-ounce bottles, which gives owners multiple containers for their marine-use routine.

Skip it if you need a stated dose per gallons of fuel; Mercury Quickleen specifies one ounce for five gallons.

A fit for marine owners who want cleaning and stored-fuel support in one treatment, including use with injectors or carburetors. Check the product label for application amounts, since the supplied listing does not state a fuel ratio.

Listed on Amazon as: Sea Foam Marine PRO Fuel System Treatment, 20 oz, Pack of 3

#6

6. Liqui Moly Marine 4T Additive

• Volume: 200 ml
• Weight: 7.84 oz
• Size: 1 Count (Pack of 1)

Best for: Port-injected and carbureted engines.

Why it ranks #6: The marine 4T additive is described for port-injected and carbureted gasoline engines and targets injectors, combustion deposits, and corrosion.

Liqui Moly Marine 4T Additive Shooter targets injectors and combustion-chamber deposits while also stating corrosion protection. Its listed fit covers port-injected and carbureted gasoline engines, and the product description connects proper fuel atomization with improved engine efficiency for owners focused on fuel-system upkeep.

Cleaning injectors and intake-valve or combustion-chamber carbon deposits gives the additive several stated targets within a gasoline engine. The claimed restoration of proper fuel atomization links injector maintenance to the listed efficiency benefit, while corrosion protection adds a separate fuel-system maintenance function. Its compatibility is specified for port-injected and carbureted gasoline engines, helping buyers check engine type against the stated scope. The 200-milliliter container is a single unit, but the supplied facts do not state a treatment ratio.

Skip it if you need a stated dose per gallons of fuel; STA-BIL 360 Marine lists one ounce per up to ten gallons.

Consider it for a gasoline outboard that is port-injected or carbureted when injector cleaning, atomization, and corrosion protection matter. Confirm the label's application directions before planning treatment, as no ratio appears in the supplied facts.

Listed on Amazon as: Liqui Moly Marine 4T Additive Shooter | 200 ML | SKU: 25102

#7

7. STA-BIL Marine Tune-Up

• Weight: 7.5 oz

Best for: Outboard storage protection.

Why it ranks #7: This marine fuel treatment is a relevant boating option, and verified product information says it protects internal components during storage.

Protection for internal components during storage is the clearest reason to consider this STA-BIL Marine Tune-Up Fuel Treatment. The 8-ounce bottle targets an off-season concern for boat owners looking to protect engine internals while equipment is stored, rather than a product listing centered on routine injector-cleaning dosage or broad fuel-system treatment.

Its stated storage-protection role makes this a focused option for owners preparing an outboard for downtime. The 8-ounce size is a compact bottle to keep with marine maintenance supplies, while the listed brand and product name identify it as a marine tune-up treatment. The supplied facts do not specify a fuel ratio or a list of components it cleans, so buyers seeking a quantified injector-cleaning routine should choose a product with those details stated.

Skip it if you need a stated injector-cleaning dose or a detailed component list; Mercury Quickleen specifies one ounce per five gallons and names the deposits it removes.

Choose it if your outboard maintenance priority is protecting internal components during storage and you want an 8-ounce marine treatment. If injector cleaning with a stated fuel ratio is central to your routine, consider a product that supplies that guidance.

Listed on Amazon as: STA-BIL Marine Tune-Up Fuel Treatment, 8 oz

#8

8. Quicksilver Power Tune

• Volume: 12 fluid oz
• Weight: 12 g
• Size: 12 Fl Oz (Pack of 1)

Best for: Spray-on internal engine deposits.

Why it ranks #8: It works with 2- and 4-cycle carbureted and fuel-injected gasoline engines, but its spray-can format is less direct for tank treatment.

Quicksilver Power Tune comes as a 12-ounce spray can with an application straw, setting it apart from pour-in fuel treatments. It removes harmful deposits from normal use and is listed for two- and four-cycle carbureted or fuel-injected gasoline engines, offering broad engine-type coverage.

The spray format and included application straw support directing the cleaner during an internal-engine cleaning task, rather than measuring a dose into a fuel tank. Its stated use spans both two- and four-cycle gasoline engines and both carbureted and fuel-injected systems. Quicksilver says removing harmful deposits can improve fuel/air flow and overall engine performance. That makes it relevant to varied gasoline outboards, while its spray application is a different workflow from routine tank additives.

Skip it if you want a pour-in marine treatment with fuel stabilization; Sea Foam Marine PRO lists both marine-system cleaning and stored-fuel support.

Choose this for owners seeking a spray-applied internal engine cleaner across carbureted and injected two- or four-cycle gasoline engines. Its application method differs from a pour-in fuel additive, so consider your maintenance workflow.

Listed on Amazon as: Quicksilver 858080Q03 Power Tune Internal Engine Cleaner for 2-Stroke, 4-Stroke and Fuel-Injected Gas Engines – 12 Oz.

#9

9. Red Line SI-1 Cleaner

• Volume: 15 fluid oz
• Size: 15 Fl Oz (Pack of 2)

Best for: Concentrated gasoline-system cleaner.

Why it ranks #9: It cleans injectors and carburetors, but the listing describes a general fuel-system cleaner rather than an outboard-specific marine treatment.

Red Line SI-1 combines high- and low-temperature detergents in a concentrated fuel-system cleaner, targeting deposits in injectors, carburetors, valves, and combustion chambers. Its listing also identifies synthetic upper-cylinder lubricant and corrosion prevention, giving gasoline-engine owners several stated maintenance functions in one treatment.

The detergent blend is specified for cleaning deposits across injectors, carburetors, valves, and combustion chambers, so the stated scope reaches beyond a single fuel-system component. Red Line says the treatment enhances gasoline stability and reduces gum and varnish buildup, supporting fuel-system maintenance alongside cleaning. The formula is also identified as containing synthetic upper-cylinder lubricant. The listing says it cleans all forms of injectors, including GDI, but does not provide an outboard-specific application direction.

Skip it if you need marine-specific application guidance; STA-BIL 360 Marine explicitly identifies in-season marine fuel-system cleaning and a measured dosing bottle.

A fit for owners seeking a concentrated gasoline-system cleaner with deposit control and upper-cylinder lubrication. Its listed features cover broad gasoline applications, but buyers prioritizing marine-specific dosing guidance should look for that direction explicitly.

Listed on Amazon as: Red Line 60103 SI-1 Complete Fuel System Cleaner, Cleans and Prevents Corrosion in Fuel Systems, Cleans Injectors, Carburetors, Valve and Combustion Chamber Deposits – 15 Ounce (2 Pack)

#10

10. Seafoam IC5 Cleaner

• Weight: 5.6 oz

Best for: Gasoline injector maintenance.

Why it ranks #10: The listing describes use in gasoline fuel-injected engines but provides no marine or outboard compatibility details, making it the least specific fit.

Seafoam IC5 focuses on cleaning injectors in gasoline fuel-injected engines, with the stated aim of restoring injector spray patterns. The listing connects cleaner injectors with recovery of lost power and fuel economy, making this a narrowly focused option for owners addressing those injector-related concerns.

Its gasoline fuel-injection restriction helps define where the product fits: it is presented for injected gasoline engines, not as a general-purpose marine cleaner. The stated spray-pattern restoration gives the cleaning claim a specific target, while the description links dirty injectors to lost engine power and fuel economy. That makes the product most relevant when those problems are associated with injector condition. The supplied facts do not give an outboard-specific dose or marine stabilization function.

Skip it if you run a carbureted outboard; Quicksilver Power Tune is listed for both carbureted and fuel-injected gasoline engines.

Consider it for a gasoline fuel-injected outboard when injector cleaning and spray-pattern restoration are the priorities. Its stated scope is narrow, so owners of carbureted engines should choose a cleaner listing that engine type.

Listed on Amazon as: Seafoam IC5 Fuel Injector Cleaner