MEILAN Spark Plugs for Marine Outboards & Inboards QL78YC 6-Pack — 14mm Thread, Projected Tip

MEILAN 6-pack spark plugs (QL78YC 24 / QL78YC-6PK) are OEM-compatible replacement plugs designed for many marine outboard and inboard engines, supplied as six standard projected-tip, 14mm-thread plugs.

These replacement spark plugs are bulk-packed and built to Champion specifications to fit a range of boats and marine powerheads. They feature a 14mm thread diameter, 12.7mm reach, a flat seat, 21mm hex for wrenching, and a projected tip with a solid terminal. Sold as a pack of six, the plugs arrive new and ready for installation — but always verify the correct part number in your engine's owner manual before fitting.

Which engines will these plugs fit?

The MEILAN QL78YC 6-pack is intended as a Genuine Champion-compatible replacement for many outboard and inboard marine engines that specify the QL78YC family. Compatibility depends on thread size, reach, and seat type rather than brand alone, so confirm cross-reference details for your model.

• Thread: 14mm — common on many small to mid-size marine engines.
• Reach: 12.7mm — matches engines requiring that electrode extension.
• Flat seat and projected tip — ensure compatibility with your combustion chamber design.

How do I install these spark plugs correctly?

Installation requires basic hand tools and attention to torque and gap. Hand-start the plug to avoid cross-threading, use the specified torque or a torque wrench, and confirm the electrode gap per your owner's manual before installation.

• Hand-thread first to prevent damage to cylinder head threads.
• Use a 21mm socket to tighten to manufacturer torque specs.
• Check or set the spark gap to the engine maker’s recommendation before fitting.

What are the plug’s key specifications and why they matter?

These characteristics determine fit, sealing, reach into the combustion chamber, and suitability for your engine’s ignition system. Matching specs prevents combustion issues, misfires, and mechanical damage.

• Type: Standard, projected-tip — positions the electrode for reliable ignition.
• Terminal: Solid — compatible with standard marine ignition leads or caps.
• Hex size: 21mm — fits common spark plug sockets for service.

Are these genuine Champion plugs and what does ‘bulk packed’ mean?

The MEILAN listing supplies the Champion-compatible part number QL78YC-6PK as a genuine replacement reference. Bulk packed means the plugs are packaged together without individual retail boxes, ideal for servicing multiple cylinders at once.

• Genuine replacement reference: QL78YC-6PK for cross-checking.
• Bulk packed: cost-efficient for mechanics or multi-plug maintenance.
• New condition: ready for immediate fitment following installation best practices.

Who is this product for? Boat owners, marine mechanics, and hobbyists who maintain outboard or inboard engines and need an economical six-pack of OEM-replacement spark plugs will find this kit useful. It’s best for anyone who has verified that their engine calls for a 14mm thread, 12.7mm reach, flat seat, and projected tip configuration. If you’re uncertain about fitment, consult your engine’s service manual or check cross-reference lists before installing.