The Buckshot Racing #77 Spark Plug Thread Chaser is a precision tool designed to clean, restore, and straighten spark plug threads in outboard cylinder heads. This tool is compatible with the majority of marine outboards using 14mm spark plugs (NGK, Champion, Denso, ect), making it an essential addition for maintenance, repair, and engine builds.
 
Manufactured in the USA, this chaser is designed with a narrow profile and extended reach, allowing access to deep or confined spark plug holes commonly found in outboard engines.
 
What a Spark Plug Thread Chaser Does
 
A spark plug thread chaser is often confused with a tap, but it serves a different purpose. Unlike a cutting tap, this tool is designed to reform and clean existing threads without removing excessive material.
 
It works by removing carbon buildup, corrosion, dirt, and minor thread distortion, helping restore proper thread engagement. This makes it ideal for preventative maintenance or light thread repair, especially on aluminum cylinder heads where preserving material is critical.
 
Using a chaser instead of a tap reduces the risk of over-cutting threads or weakening the cylinder head.
 
Wide Fitment Across Outboards Motors
 
The M14 x 1.25 spark plug thread chaser fits a wide range of Mercury, Mariner, OMC (Johnson/Evinrude), and Yamaha outboards, as well as many other marine and powersports engines that use standard 14mm spark plugs.
 
Common Applications
 
Mercury 2-stroke V6 outboards (2.0L, 2.4L, 2.5L, and 3.0L) including 135, 150, 175, 200, 225 Pro Max, 260 EFI, 280 ROS, and 300 Drag, as well as many Mercury 4-stroke models.
 
It is also compatible with OMC Johnson/Evinrude V4 and V6 outboards, along with Yamaha 2-stroke and 4-stroke engines that utilize 14mm spark plug threads.
 
Because M14 x 1.25 is the industry standard, this tool is suitable for most outboard engines on the market, making it a versatile solution for marine technicians and performance builders.
 
Designed for Hard-to-Reach Spark Plug Holes
 
Outboard cylinder heads often have deep or restricted spark plug access, especially on high-performance engines and tight cowling configurations.
 
This thread chaser features a slim body and extended length, allowing it to reach into confined areas where standard tools may not fit. It can be used with a 3/8-inch ratchet or extension, providing additional leverage when needed.
 
Proper Usage and Best Practices
 
To achieve the best results, proper technique is important. Before use, apply a small amount of anti-seize, engine oil, or grease to the threads of the chaser. This helps capture debris and prevents galling during use.
 
The piston should be positioned away from the spark plug hole (bottom dead center) to reduce the risk of debris entering the combustion chamber.
 
The tool should be inserted carefully and threaded in by hand first, ensuring proper alignment. Rotate clockwise while occasionally backing off slightly to clear debris, continuing until the threads are fully cleaned.
 
For stubborn threads, a 3/8-inch ratchet can be used while maintaining straight alignment.
 
Prevent Costly Repairs
 
Damaged or dirty spark plug threads can lead to poor sealing, misfires, or stripped threads, which may require costly repairs such as thread inserts or cylinder head replacement.
 
Using the Buckshot Racing #77 Spark Plug Thread Chaser as part of regular maintenance helps extend thread life, improve spark plug seating, and prevent future damage.
 
Built for Marine Performance and Reliability
 
From routine maintenance to performance engine builds, the Buckshot Racing #77 Spark Plug Thread Chaser is a must-have tool for keeping spark plug threads clean and serviceable.
Designed for Mercury, OMC, Yamaha, and most 14mm spark plug applications, it delivers a reliable, professional solution for maintaining cylinder head integrity in demanding marine environments.

Contact mike@buckshotracing77.com with any questions.