- Boat Marine Engine Cylinder Compression Gauge Test Tester Tool
- Perfect for Hard to Reach Bottom Plug Holes on Older Mercury Models.
- For use with:
- Fits a 3/4 in.-16 Spark Plug Hole.
- Manufacturer: Sierra
- Model Number: Compression Tester
- Part Number: 18-9800
- Also Known As: Mallory 9-79804