Sizing the run from your landside breaker panel out to the boat lift control box / motors. Long dock runs eat voltage — under-sized wire makes motors hum, stall, and trip breakers. Target: ≤ 3% drop for motor branch circuits.
Use the motor nameplate FLA × number of motors. Typical Deco 3/4 HP @ 220V draws ~6–8 A per motor running; size for total connected load.
Measure the actual conductor path, not the straight line. Add length for risers, loops, and slack.
Recommended
10 AWG copper
5.59 V drop (2.54%) at 15 A over 150 ft on a 220 V circuit.
| Gauge | V drop | % drop | Ampacity |
|---|---|---|---|
| 14 AWG | 14.13 V | 6.42% | 20 A |
| 12 AWG | 8.89 V | 4.04% | 25 A |
| 10 AWG | 5.59 V | 2.54% | 35 A |
| 8 AWG | 3.52 V | 1.60% | 50 A |
| 6 AWG | 2.21 V | 1.01% | 65 A |
| 4 AWG | 1.39 V | 0.63% | 85 A |
| 2 AWG | 0.87 V | 0.40% | 115 A |
| 1/0 AWG | 0.55 V | 0.25% | 150 A |
| 2/0 AWG | 0.44 V | 0.20% | 175 A |
How to read this
- Green rows are within the 3% target for motor branch circuits.
- Yellow rows are 3–5% — workable but motors will start sluggish.
- Dim rows are either over 5% drop or over the wire's ampacity (!).
- Formula: VD = 2 × K × I × L ÷ CM (single-phase, K = 12.9 for copper at 75°C). For aluminum, voltages and gauges differ — size up one or two AWG.
- This is a sizing aid. Final conductor selection must follow your local electrical code (NEC 310 ampacity tables, derating for conduit fill, temperature, and any GFCI / disconnect requirements for marine installs).