100TECH Fuel/Water Sender: ID via top aluminum cap number. Standard 2 wires (blue=ground, brown=gauge). Non-100TECH replacement needs tank/sender depth, ohm range, mounting. Stem: 316 SS; float: NBR. Outputs: 240-33Ω (US), 0-190/0-90Ω (stock); others via sales.

100TECH gauges have IP67 (dust-tight, water-resistant) via premium materials, sealed design. Most gauges corrode from moisture; location affects lifespan. 100TECH works in harsh marine/industrial environments.

Two methods to check gauge function & US/EU spec: test back wires or wiring loom. US gauge shows EMPTY (off)→FULL (ground); EU opposite. Test confirms function and spec.

US fuel specs: 240Ω (empty)-33Ω (full); EU: 0Ω (empty)-190Ω (full). Sender & gauge must match—wrong gauge (e.g., 240-33Ω for 0-190Ω sender) causes reverse readings, even with correct wiring.

Boat fuel gauge reads backwards mostly from wrong type (240-33Ω vs 0-190Ω sender/gauge mismatch). Test old sender with multimeter or use resistors (33Ω, 243Ω, 191Ω) to confirm needed type.