Here’s how to install a battery-powered electric trolling motor that can be easily removed for space and weight.
Bow-mounted electric trolling motors are standard gear aboard fishing boats of all sizes and styles these days, and they are handy for use in many fresh- and saltwater fishing situations. The downside is the weight and space the motors and their batteries consume, and not all fishing conditions call for employing the alternative bow propulsion.
We faced just such a dilemma with our 20-foot center-console, which we use for freshwater, coastal, and offshore angling, and we often don’t need the electric motor option. We can make better use of the space, both up top and below, and get better mileage, while trailering and underway, without the weight associated with the bank of batteries and dedicated charger required to operate an electric motor.
The solution was rigging a portable setup that allows us to easily remove the electric motor, batteries, and charger when we don’t need them, yet install the system with a minimum amount of effort when we do want the bow-power option. A side benefit of the portable setup is that the standalone forward charger keeps the electric motor’s batteries and charging system separate from the starting and house battery bank. Those batteries are mounted under the helm console and use a permanently mounted on-board charger, also located under the steering console, to maintain a charge.
When developing the setup, we considered the usual amount of time we use a bow-mounted motor and what thrust we actually needed to adequately maneuver the 20-footer. We determined that a 24-volt model offering 80 pounds of thrust would fit our needs, based on how we use our boat, while reducing the weight of the batteries that we would need to mount and, to a lesser degree, the weight of the motor itself. Because the bow of the boat was already fitted with a standard quick-release mount for a Minn Kota electric motor, we chose a Minn Kota Riptide Ulterra 80 model.
To take advantage of their weight-to-power ratio, smaller footprint, and the fact that, unlike lead-acid batteries, there’s very little if any likelihood of gassing during the charging process, we chose AGM batteries. Lead acid batteries could gas and, in proximity with a cheap, nonmarine-grade battery charger that is not ignition-protected, there’s a greater likelihood of explosion or, at the very least, damage to the battery charger from the gas. Even with the proper marine-grade components, the venting point cannot be stressed enough: The batteries and charger must be properly ventilated during the charging process.
Both overcharging and undercharging a marine battery will reduce the battery’s lifespan and degrade its performance.
As for the specific AGM batteries, we chose a pair of West Marine Group 27 Dual Purpose (WM8A27M) cells to power the bow-mounted motor as well as for the boat’s starting and house batteries to keep the system as consistent as possible in the event we ever need to swap out a battery from either of the separate setups. To charge the batteries we selected a Minn Kota (MK 210D) two-bank digital onboard charger.
The result has worked very well, allowing the boat to be extremely adaptable and efficient to trailer and operate. With a total weight of a little over 200 pounds (63 lbs. per battery, 11 lb. charger, and 65 lb. motor) the space and savings gained when the portable rig is removed are notable. That said, the system is worth its weight in fillets when fishing conditions call for a bow-mount motor option, and with the boat so rigged, it’s an easy op to exercise. Here are the major steps we took to rig the boat for part-time bow-mount motor use.
Difficulty: Moderate (some McGuyvering may be involved)Materials & Tools:
- Milk crate
- Wood shims
- TRAC cable
- Connect-Ease quick-release wiring harnesses
- Battery strap
- Ignition-proof marine grade onboard battery charger
- AGM batteries
- Wire stripper/crimper
Time: 3 hours
Cost: About $500 depending on battery and charger choices (not including motor)
1. We started by identifying a portable way to secure the pair of AGM batteries inside the large bow locker that ventilates via the adjoining anchor locker and the gunwales. To further the ventilation process, we set the batteries in a rectangular, open-sided milk crate and separated the cells with a section of pressure-treated pine two-by-fours. They fit like a glove in the crate that offered ready-made handholds for lifting and carrying and open sides for ventilation. The crate straddled two stringers in a snug spot that required minimal bracing to secure in place and offer air flow below the batteries.
2. We installed battery strap webbing fitted with a quick-release buckle to stringers on either side of the crate to secure it in place and threaded posts for securing the cover on our DIY battery box. We sealed all screw holes that were in wood with marine-grade silicone.
3. A rectangle of Plexiglas serves as a protective cover over the crate, allowing us to easily check the batteries and connections. Securing the battery charger to the cover created a portable, self-contained battery and charger unit. When charging, it is important to lift the lid for maximum ventilation.
4. TRAC high-current connectors and 50-amp sealed thermal circuit breakers in the wiring between the batteries and the motor allow easy hookups and protect the wiring and motor. Any positive terminals were appropriately covered.
5. Following ABYC standards, the forward charger plugs into a marine-grade 12-gauge power cord labeled as AC. It leads aft under the deck to the Minn Kota AC Power Port Saltwater receptacle on the starboard side of the helm console. We checked for any possible abrasion points along the route and secured the cable. The plugged connection is mounted to an interior bulkhead and further protected with a water-resistant cover.
6. Because the project boat’s bow was already fitted with a Minn Kota quick-release mounting base for a standard Riptide bow-mounted motor and convertible rail cutout, all we had to do to accommodate the Ulterra was trim part of the poly base we had already mounted to allow the slightly larger motor to fully deploy. Minn Kota offers a mounting plate specifically designed for the Ulterra that we could have used instead. The quick-release allows us to remove the motor to eliminate obstruction of the bow running lights if we want to operate the boat between sunset and sunrise. An option is rigging a plug-in post-mount that would raise the bow navigation light above the motor to permit use after dark.
7. The Minn Kota Heading Sensor, which provides boat heading information to the Bluetooth-compatible i-Pilot Link-equipped Ulterra, is mounted atop the starboard gunwale and the power cable run underneath the deck aft to the boat’s house battery.
8. The Ulterra’s wireless remote control allows us to stow, deploy, and operate the bow-mounted motor from anywhere on the boat – or nearby dock – and the i-Pilot Link offers several fishing and control features with its interface with the boat’s Humminbird Helix 10 fishfinder. When we do not wish to have the option of a bow-mounted electric motor, it takes less than 5 minutes, and at least one strong back, to disconnect the battery and charger wiring, lift the battery/charger combo out of the locker and remove it, and release the bow-mounted motor, from the boat. You have the option of lifting each battery separately or, if you have a strong back or an extra hand, both at once using the grips on the crate.
West Marine Group 27
Dual Purpose AGM Batteries
Group size: 27
Amp hours (Ah): 92
Cold cranking amps (CCA): 580
Marine cranking amps (MCA): 900
Reserve minutes: 175
Weight (each): 63 lbs.
Dimensions: 12.75″L x 6.75″W x 9.875″H
Minn Kota MK 210D 2 Bank Charger
Charging Banks: 2
Amps Per Bank: 5
Total Amp Output: 10
Weight: 11 lbs.
Dimensions: 11.5″ x 7.5″ x 4″
Weight: 11 lbs.
Kota Riptide Ulterra 80
with i-Pilot Link
Max thrust: 80 lbs.
Shaft length: 60″
Weight: 65 lbs.