Best Spark Plugs For Mercury 2 Stroke Outboard

#1 · Best Overall

1. NGK 6431 BU8H

• Core Material: Copper
• Compatible with Vehicle Type: Watercraft
• Thread Size: M14 – 1.25

Best for: Six-plug BU8H marine set.

Why it ranks #1: The six-pack is identified for numerous Mercury and Mariner models, and its BU8H surface-gap design is described for marine outboards.

Surface-gap electrode construction is the defining feature of this six-pack, giving Mercury and Mariner owners a matching set of NGK BU8H plugs for compatible outboards. Its extensive listed engine coverage includes several 2.5L and 3.4L Mercury applications, making it a practical option when those models match your engine.

The surface-gap design is identified for marine outboard use, while the copper core provides the listed core material for this NGK plug. Six plugs arrive together, which supports a multi-cylinder service without assembling a set from individual listings. The stated M14 – 1.25 thread size and named Mercury and Mariner applications help narrow the selection, but the specific engine model still needs to match the supplied compatibility list and owner’s manual.

Skip it if you need a single replacement plug; Quicksilver 13686Q is sold as one BU8H plug.

A Mercury or Mariner owner with a listed compatible model and a multi-plug service in mind gets a six-piece NGK BU8H set. Treat the named engine coverage as the boundary, rather than assuming universal outboard fit.

Listed on Amazon as: NGK 6431 BU8H Spark Plug – Fits Mariner Mercury Outboard (6 pack)

#2 · Semi-Surface Design

2. Quicksilver 13686Q BU8H

• Core Material: Copper
• Compatible with Vehicle Type: Watercraft
• Thread Size: M14x1.5

Best for: Single BU8H OEM-style plug.

Why it ranks #2: This Quicksilver plug uses NGK BU8H semi-surface discharge construction and copper core, with guidance to follow the engine manual.

A semi-surface discharge design gives this single Quicksilver BU8H plug its specific maintenance focus: the listing says it can burn off carbon before deposits foul the plug. It is an NGK marine outboard plug for buyers whose engine manual calls for this type and application.

Small side electrodes are pre-gapped and do not require gap adjustment, simplifying installation compared with a plug that needs manual adjustment. The copper core aids heat removal, and the trivalent metal plating is described as providing marine corrosion resistance and easier removal through anti-seizing properties. Quicksilver states that its products match Mercury Marine original-equipment performance specifications. The listing supplies one plug, so multi-cylinder maintenance requires additional units.

Skip it if you need a six-plug BU8H set; NGK 6431 BU8H is listed as a six-pack.

This suits a Mercury or other marine-outboard owner whose manual specifies BU8H and who needs one replacement plug with pre-gapped electrodes. Its single-plug quantity and manual-based fit requirement make it less suited to bulk servicing.

Listed on Amazon as: Quicksilver 13686Q NGK BU8H Semi-Surface Discharge Spark Plug for Marine Outboard Engines, 1 Pack

#3 · Six-Plug BU8H Set

3. Generic BU8H 6431

• Core Material: Copper
• Compatible with Vehicle Type: Watercraft
• Thread Size: RM

Best for: Pre-gapped BU8H six-pack.

Why it ranks #3: The six-plug pre-gapped, non-resistor BU8H kit lists Mercury and Mariner applications, including several outboard horsepower models.

Pre-gapped, non-resistor BU8H plugs are the defining combination in this six-piece kit for listed Mercury and Mariner outboards. The listing names applications such as Mercury 135 and Mariner 135 Marathon, so buyers can compare the specific engine against a familiar BU8H replacement designation.

The kit supplies six copper-core plugs, supporting a multi-cylinder replacement with one matching set. Its product description identifies the plugs as pre-gapped and non-resistor, potentially simplifying preparation when those specifications match the engine requirement. Compatibility details include selected Mercury and Mariner horsepower applications and model years, rather than a universal claim. The thread specification is listed as RM, so buyers should compare the full plug designation and engine manual before installation.

Skip it if you need NGK-branded BU8H plugs; NGK 6431 BU8H offers the same plug designation in a six-pack.

This is a practical choice for owners whose manual calls for a pre-gapped, non-resistor BU8H plug and whose engine appears in the listed applications. Its six-piece quantity is useful for service, while model-specific fit remains essential.

Listed on Amazon as: (6x) BU8H (6431) Non-Resistor Spark Plug Pre-Gapped Compatible With Mercury & Mariner

#4 · Broad Two-Stroke Fitment

4. BDFHYK 4495 Iridium

• Core Material: Iridium
• Compatible with Vehicle Type: Watercraft
• Thread Size: 20.4mm

Best for: Iridium 4495 replacement set.

Why it ranks #4: Its compatibility list explicitly includes Mercury 2-stroke engines and many horsepower classes; the plugs have iridium cores and a listed 1-millimeter gap.

Iridium is the central material feature of this four-pack, which lists Mercury outboard compatibility for a broad range of engine sizes and named families. The seller describes faster, more sensitive ignition jumps, offering buyers seeking a 4495 replacement an application-specific alternative to conventional plug materials.

The 1-millimeter gap and 20.4-millimeter thread size provide concrete specifications to compare against the required plug, while the iridium core and top identify the electrode material. BDFHYK lists compatibility across Mercury 2-stroke engines including 20, 30, 40, 50, 60, 80, 115, and 125, along with Jet and Sea Pro variants. Four plugs make this a set for servicing more than one cylinder, but compatibility should follow the complete listing and engine requirements.

Skip it if you need six BU8H plugs; NGK 6431 BU8H supplies a six-piece set.

Choose this set if your Mercury outboard calls for the listed 4495 replacement and iridium plugs, and the 20.4-millimeter thread and stated gap suit the application. Its four-piece quantity is the practical limit for larger service needs.

Listed on Amazon as: BDFHYK 4 Pack Iridium Spark Plugs Replacement for 4495 BPZ8HN10

#5

5. YUXIVCNE QL78YC

• Core Material: Copper
• Compatible with Vehicle Type: Johnson, Evinrude, Mercury Outboards Inboard…

Best for: QL78YC marine six-pack.

Why it ranks #5: The six-pack lists Mercury outboards and replacement number BPZ8HS10, plus detailed horsepower and year coverage for several other marine brands.

A six-plug QL78YC set with copper cores targets marine-engine owners looking for replacements across selected Johnson, Evinrude, and Mercury applications. Its listing also identifies BPZ8HS10 and several other replacement numbers, giving buyers multiple reference points when matching a plug to an existing specification.

The copper core and nickel top are the listed materials, while the six-piece quantity supports servicing a multi-cylinder engine with a single set. Compatibility facts specify several Johnson and Evinrude horsepower ranges and identify Mercury outboards among supported applications. That broad marine scope can help buyers comparing replacement numbers, but the supplied Mercury details do not name a complete model-by-model range. Match QL78YC or its listed equivalents to the engine’s required plug.

Skip it if you need named Mercury horsepower applications; yeeluzan QL78YC lists specific Mercury sizes and models.

This set fits buyers whose marine engine specifies QL78YC or a listed replacement number and who want six plugs together. Its Johnson and Evinrude coverage is more specifically detailed than its Mercury fitment, so verify the required designation.

Listed on Amazon as: YUXIVCNE 6 Pack Spark Plugs QL78YC 938M Replacement for Johnson Evinrude for Mercury Outboards Inboard Marine Engines Parts Replace BPZ8HS10

#6

6. yeeluzan QL78YC

• Core Material: Iridium
• Compatible with Vehicle Type: Outboard Engine

Best for: Eight-plug QL78YC set.

Why it ranks #6: This eight-pack lists Mercury compatibility for selected engines and QL78YC-related replacement numbers, though the Mercury application list is limited.

Eight iridium plugs make this QL78YC replacement set notable for buyers servicing several compatible engines or cylinders at once. Its listing names Mercury applications including 9.9 HP, 10 HP Magnum Marathon, 20 HP, 20 Jet, and 50 HP, alongside specified Johnson and Evinrude models.

The iridium core and iridium top material identify the plug construction, while the eight-piece quantity supplies a larger set than many individual replacement listings. QL78YC is tied to a long list of replacement numbers, including 0437929 and BPZ8HS10, which can help buyers compare against an existing plug specification. Mercury coverage is limited to the specific engine applications named here; the wider Johnson and Evinrude list does not establish fit across other Mercury 2-strokes.

Skip it if you need a BU8H plug for a listed Mercury 135 or 150; NGK 6431 BU8H names those models.

Consider this set when the engine calls for QL78YC or a listed replacement number and is among the named applications. The eight-piece quantity suits broader servicing, but the Mercury fitment list is narrower than its other-brand coverage.

Listed on Amazon as: 8PCS Iridium Spark Plugs Replaces QL78YC For Mercury Outboard Engines

#7

7. SYKRSS 4838 Iridium

• Core Material: Iridium
• Compatible with Vehicle Type: Watercraft
• Thread Size: RM

Best for: Iridium 4838 Mercury range.

Why it ranks #7: The four-pack lists compatibility across Mercury and Mariner horsepower ranges and identifies replacement numbers 4838 and BP8H-N-10.

Iridium construction and a four-plug quantity define this SYKRSS 4838 set for Mercury and Mariner outboard owners. Its compatibility listing spans named horsepower applications from 6.0 to 125 hp and identifies 4838 and BP8H-N-10 as replacement references for buyers matching an existing plug.

The iridium core and top material distinguish this plug, while the stated 1-millimeter gap and RM thread provide specifications to check against the engine’s required plug. Four plugs support a multi-cylinder service, and the Mercury and Mariner list includes applications such as 25, 40, 60, 80, 115, and 125 hp. The listing directs buyers to further fitment details, so the broad horsepower range should not replace checking the exact engine and plug requirement.

Skip it if you need six BU8H plugs for a Mercury 150; NGK 6431 BU8H names 150 hp applications and comes in six.

This suits a Mercury or Mariner owner whose engine matches the listed 4838 applications and calls for the stated iridium plug. The four-piece quantity and need to verify exact fitment set its practical boundaries.

Listed on Amazon as: Iridium Spark Plug 4838 4 Pack for Mercury Outboard

#8

8. Quicksilver 827858Q DPR6EA-9

• Core Material: Copper
• Compatible with Vehicle Type: Watercraft
• Thread Size: RM

Best for: Single DPR6EA-9 copper plug.

Why it ranks #8: This copper-core NGK standard plug meets Mercury Marine specifications, but the data does not specify a 2-stroke outboard application.

Pre-gapping to the engine manufacturer’s specifications is the practical feature of this single Quicksilver DPR6EA-9 plug. Its listing says it meets Mercury Marine original-equipment specifications and identifies a copper core, making it a focused option when the engine manual specifies this exact plug.

The factory-specified pre-gap can reduce setup work before installation, while the copper core promotes heat dissipation and efficient plug operation, according to the listing. A threaded terminal completes the described construction. Quicksilver states that its products match Mercury Marine original-equipment performance specifications, adding a brand-specific reference for buyers comparing replacements. Only one plug is included, so owners servicing multiple cylinders need to obtain additional units; the owner’s manual remains the stated guide to the correct plug.

Skip it if you need one BU8H plug rather than DPR6EA-9; Quicksilver 13686Q is the single-plug BU8H option.

Choose this single plug when the Mercury or MerCruiser engine manual calls for DPR6EA-9 and a pre-gapped copper-core replacement is appropriate. Its exact plug designation and one-piece quantity define the fit and service boundary.

Listed on Amazon as: Quicksilver 827858Q NGK DPR6EA-9 Standard Copper Core Spark Plug for Mercury Marine and MerCruiser Engines, 1 Pack

#9

9. Quicksilver 8M0157328 LFR4A-E

• Core Material: Copper
• Compatible with Vehicle Type: Car, Truck
• Thread Size: RM

Best for: V-Power LFR4A-E replacement.

Why it ranks #9: The listing says it meets Mercury Marine specifications and comes pre-gapped, but it provides no specific 2-stroke outboard fitment.

NGK’s V-shaped center-electrode cut is the defining feature of this LFR4A-E plug; the listing says it directs the spark toward the electrode edge to aid spark development and ignitability. It is identified as a Quicksilver plug meeting Mercury Marine OEM specifications.

The listed copper core and V-Power electrode design connect the plug’s material and shape to the stated ignition function. It comes pre-gapped to the engine manufacturer’s specification, although the description recommends checking the gap before installation. Quicksilver states that its products match Mercury Marine original-equipment performance specifications, but the supplied vehicle-type field says car and truck. Use the engine manual’s exact plug designation as the fitment authority before selecting this item for an outboard.

Skip it if you want a plug explicitly categorized for watercraft; Quicksilver DPR6EA-9 lists watercraft compatibility.

This may suit an owner whose manual specifically calls for LFR4A-E and who values the V-Power electrode and pre-gap. The car-and-truck vehicle-type entry makes manual-based confirmation particularly important for outboard use.

Listed on Amazon as: Quicksilver 8M0157328 NGK LFR4A-E Standard Spark Plug (6499)

#10

10. Micro Traders DCPR6E

Best for: Two-plug DCPR6E replacement.

Why it ranks #10: The two-plug listing broadly mentions Mariner and Mercury outboards but gives no engine models or 2-stroke-specific fitment.

The DCPR6E designation, also listed as DCPR6-E and 3481, is the key matching detail in this two-plug set for selected Mariner and Mercury outboards. Its stated 12-millimeter thread and 75.5-millimeter overall length give buyers measurements to compare with their engine specifications.

Two plugs make this a small replacement set, while the named model references help identify the intended plug family. The listing describes ignition for marine environments and connects it with efficient fuel combustion and smoother engine operation. Thread size and overall length offer concrete checks before installation, but the provided information does not identify specific Mercury horsepower models. Match the DCPR6E designation and dimensions to the engine’s requirements rather than relying on brand-level compatibility alone.

Skip it if you need named Mercury horsepower fitment; NGK 6431 BU8H lists specific Mercury and Mariner models.

This is for buyers whose outboard specifications call for DCPR6E, DCPR6-E, or 3481 and match the listed dimensions. Its two-plug quantity and lack of named horsepower applications make exact specification matching especially important.

Listed on Amazon as: 2pcs Spark Plug DCPR6E DCPR6-E 3481 for Outboard Engine Compatible with Mariner Mercury Models