24V vs 36V Trolling Motor Wiring: How to Wire It Right
Published May 12, 2026 · Boat Electrical · Factory-Authorized Insights
The voltage jump from 12V to 24V or 36V trips up more boat owners than any other electrical project we see. Wrong wiring damages your motor, kills batteries fast, or causes fires. Here’s the right way.
Why Higher Voltage at All?
Two reasons: more thrust, longer run time.
For a given motor power output:
- 12V = high amp draw → faster battery drain, more voltage drop, hotter wiring
- 24V = moderate amp draw → moderate run time, modest voltage drop
- 36V = low amp draw → long run time, minimal voltage drop, cooler operation
A 112-lb-thrust 36V motor draws roughly half the amps of an equivalent 56-lb 12V motor — even though it’s twice as powerful. That’s the whole point.
The Wiring Concept: Series vs Parallel
This is the part most DIYers get wrong.
Series wiring (used for higher voltage):
- Connect + of battery 1 to − of battery 2
- The remaining + and − terminals become your system + and −
- Voltage adds: two 12V batteries in series = 24V
- Amp-hour capacity stays the same
Parallel wiring (used for higher capacity):
-
- to +, − to −
- Voltage stays the same
- Amp-hour capacity adds: two 12V 100Ah in parallel = 12V 200Ah
For trolling motors, you use series to get 24V or 36V from multiple 12V batteries. Never parallel batteries for trolling motor use unless you’re trying to extend a single-voltage bank capacity.
24V Wiring Diagram (Two Batteries)
POSITIVE LEAD TO MOTOR (+)
|
[+] ━━ BATTERY 1 ━━ [−]
|
(JUMPER WIRE — series link)
|
[+] ━━ BATTERY 2 ━━ [−]
|
NEGATIVE LEAD TO MOTOR (−)
Wiring sequence:
- Battery 1 positive (+) → motor positive lead AND charger lead 1 positive
- Battery 1 negative (−) → Battery 2 positive (+) [series jumper]
- Battery 2 negative (−) → motor negative lead AND charger lead 2 negative
- Inline circuit breaker on the positive lead near the battery, before it reaches the motor
36V Wiring Diagram (Three Batteries)
POSITIVE LEAD TO MOTOR (+)
|
[+] ━━ BATTERY 1 ━━ [−]
|
(series jumper to B2)
|
[+] ━━ BATTERY 2 ━━ [−]
|
(series jumper to B3)
|
[+] ━━ BATTERY 3 ━━ [−]
|
NEGATIVE LEAD TO MOTOR (−)
Same concept: positive of B1 is system positive, negative of B3 is system negative, middle batteries are linked positive-to-negative.
Wire Gauge — This Is Where People Mess Up
Voltage drop costs you thrust. Undersized wire = motor doesn’t get full voltage even with fresh batteries.
Recommended gauges (Minn Kota / MotorGuide manufacturer specs)
| Voltage | Motor thrust | Min wire gauge (under 10 ft run) | Min wire gauge (10-25 ft run) |
|---|---|---|---|
| 12V | 30-55 lbs | 8 AWG | 6 AWG |
| 24V | 55-80 lbs | 8 AWG | 6 AWG |
| 36V | 80-112 lbs | 8 AWG | 6 AWG |
| 36V | 112 lbs (max) | 6 AWG | 4 AWG |
Florida note: Use tinned marine-grade copper wire, not the cheaper bare copper auto wire. Salt and humidity corrode untinned wire from the inside.
The series jumpers between batteries
Use the same gauge as your main motor leads. Don’t use smaller wire here just because it’s a short run — current is the same throughout the circuit.
Circuit Breaker / Fuse
Required, not optional. Manufacturer specs:
| Motor amp draw | Breaker rating |
|---|---|
| Up to 30A | 50A breaker |
| 30-50A | 60A breaker |
| 50-70A | 80A breaker |
| 70+ A | 100A breaker (some need 110A) |
Minn Kota and MotorGuide each publish exact specs by model. Match it.
Why this matters: If a wire shorts (boat trailer accident, prop hitting something), the breaker trips before the wire melts and starts a fire. Without a breaker, you have an unprotected battery feeding fire potential. Boats have burned to the waterline over this.
The Charger
This is where new 24V/36V owners often get it wrong.
You need an onboard multi-bank charger
A 24V system needs a 2-bank charger — one charging output per battery, charged individually.
A 36V system needs a 3-bank charger — three charging outputs.
Why not just charge the batteries in series? Because batteries in a series bank discharge unevenly. One battery always ages faster. Charging in series leaves the weak one undercharged and the strong one overcharged. Both die fast.
A multi-bank charger gives each battery its own optimized charge cycle.
Charger sizing
| Bank size | Recommended amp output |
|---|---|
| 100 Ah single | 10-15A charger |
| 2x 100 Ah (24V system) | 2 bank × 10-15A |
| 3x 100 Ah (36V system) | 3 bank × 10-15A |
Higher amp = faster charging, but also more stress on batteries. 10A per bank is a good balance for most users.
Common Wiring Mistakes (We See Weekly)
1. Mixed battery chemistries
Lead-acid + AGM + lithium in the same series bank = ALL of them die fast. Match types. Match brands. Match ages within a year if possible.
2. Old battery + new battery in same series bank
Same problem. The weak one drags the strong one down. Replace all batteries in a bank at the same time.
3. Wrong polarity on charger
Reversed leads = damaged charger + damaged batteries. Color-code your wires clearly. Red = positive ALWAYS.
4. Loose connections
A loose nut on a battery terminal creates a high-resistance hotspot. Hotspots melt insulation, blacken terminals, and eventually arc. Torque battery terminals to 6-8 ft-lb (manufacturer-specific — don’t over-tighten).
5. Series jumpers too small
Owner uses #14 wire for the jumper between batteries because “it’s a short run.” Wrong — same current flows. Use proper gauge for the WHOLE circuit.
6. No inline breaker
Skipping the breaker is the most common cause of trolling motor electrical fires we hear about.
7. Battery box without ventilation
Lead-acid (especially flooded) outgas hydrogen. Sealed boxes without vents accumulate explosive gas. Lithium doesn’t have this problem but the precaution is universal.
8. Lithium swap with old lead-acid charger
A lead-acid charger doesn’t fully charge a lithium battery and can damage the BMS. Replace the charger when going to lithium.
What We Charge for a Done-Right Install
| Service | Cost |
|---|---|
| 24V system install (motor + batteries + breaker + charger) | $400-700 labor |
| 36V system install | $500-900 labor |
| Lithium conversion (rewiring + new charger) | $300-600 labor |
| Wiring audit + rewiring of existing system | $250-500 labor |
Parts (wire, terminals, breakers, lugs) are typically $80-200 additional depending on run length and quality.
Lithium Notes
If using LiFePO4 lithium batteries:
- Smaller wire is OK because the chemistry handles higher current cleanly — but go marine-grade tinned regardless
- Charger MUST be lithium-compatible
- BMS (built into lithium) protects against over-discharge — but a circuit breaker is still required for fault protection
- Don’t mix lithium and lead-acid in any configuration
Final Check Before You Fish
After any wiring work:
- Visual inspection — all terminals tight, no exposed copper
- Voltage at the motor lead — should match battery bank voltage (24V or 36V)
- Voltage under load — start the motor, measure at the lead. Should drop less than 5%
- Heat check — run motor for 5 minutes. Wires, terminals, breaker should be cool to touch
- Charger test — plug in, confirm each bank shows a charging indication
If anything is wrong, fix it before you launch.
Have Us Do It
Most owners don’t want to mess with this. We do these installs every week and have parts in stock.
📞 (813) 380-5145 — schedule a wiring install or audit.
Learn about our installation services → · Boat Electrical →
About Nature Coast Trolling Motors
We're a Minn Kota Authorized Service Center and a MotorGuide Certified Service provider in Plant City, FL. We repair, install, and service every major trolling motor brand for anglers across Plant City and the surrounding Tampa Bay area.