Oppama Pulse Engine Tachometer/Hour Meter PET-304 - Echo G310000050

What It Is

The Oppama PET-304 is a pulse-type engine tachometer and hour meter designed for outdoor power equipment. It’s used to set precise idle and high-speed RPMs and track engine runtime for maintenance intervals on small gas engines.

Fitment & Compatibility

• Engine type: Works on 2-stroke and 4-stroke engines with spark plug wires (gasoline only). Not for diesel or battery-powered equipment.
• Wiring: Connects by wrapping the pickup lead around the spark plug wire—no permanent wiring or battery needed.
• OEM cross-reference: Echo part number G310000050. Direct replacement for Echo, Shindaiwa, and many other brands using this Oppama module.
• Measurement check: Unit reads from 200 to 9,990 RPM. Verify your equipment’s max RPM falls within this range (most mowers, trimmers, and chainsaws do).
• Physical fit: Compact 2.2 x 1.5 x 0.7 inch body. Mounts with included double-sided tape or zip ties. Ensure you have a clean, dry spot near the spark plug wire.

Key Things to Know

• No battery needed: Runs on internal lithium cell (non-replaceable) rated for 5+ years. Unit is sealed—do not open.
• Installation difficulty: Very easy. Wrap the inductive pickup around the spark plug wire, secure the unit, and start the engine. No tools required.
• Accuracy: Pulse counting is accurate within ±1% at steady RPM. Not for transient or rapid throttle blips.
• Common gotcha: On some engines with resistor-type spark plugs, the signal may be weak. If the tachometer shows erratic readings, try a different position along the plug wire or use a non-resistor plug.

Should You Buy It

Buy this if you tune small engines professionally or want to precisely set carburetor mixtures and idle speeds on Echo, Shindaiwa, or similar equipment. It’s overkill for a single homeowner mower but valuable for anyone maintaining multiple machines or needing accurate hour tracking.