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June 05, 2008

Troll Control

An inshore fisherman's guide to electric motors

What kind of mounting mechanisms work best?
According to both manufacturers, the vast majority of saltwater anglers like to remove their trolling motors more frequently than their freshwater counterparts. That may be due to the fact that saltwater anglers target many different species in widely varied habitats. That may also result from security issues.
 
MotorGuide makes a removable mounting plate that allows anglers to   take the motor off the boat in about 20 seconds. Minn Kota, too, offers a quick-release system.
 
Those who work as saltwater fishing guides or fish frequently in tournaments demand mounts that make deployment and retrieval of the motor simple and effortless - since they may be required to change locations repeatedly throughout the day.
 
Both companies say their mounts allow for single-handed stowing and deployment. And in fact, Minn Kota's lift-assist technology uses a gas-charged spring to reduce lifting weight by 50 percent.
 
Minn Kota has also just announced the debut of its new Riptide SF, which will be available this fall. The company took its most popular Riptide Pro model - a hand-control bow-mount motor - and redesigned its arm, the portion of the motor between the shaft and the mount on which the unit rides as it deploys and stows.
 
Instead of using what's called a four-bar linkage, which features four hinge points susceptible to noisy twisting and wear, the engineers created a single- or mono-arm design. The unit also employs a new technology that applies tension on the motor in both stowed and deployed positions, reducing noise, steering torque and motor play, especially on higher-thrust models.

What does the term "amp draw" mean?
Trolling motors draw varying amperage at different speeds. Anglers can calculate their running time at full power by using the motor's amp draw (at full speed) and the battery's amp-hour rating.
 
A single 120-amp-hour, 12-volt battery and a 12-volt trolling motor drawing 30 amps at the highest speed setting will run for about 3.4 hours, according to Minn Kota figures.
 
The formula goes like this: 0.85 x   (battery amp-hour rating) = (hours of operation) x (motor amp draw).
 
That same motor may draw only 5 amps at the slowest speed, where it may run for more than 20 hours.

Aren't trolling motors susceptible to corrosion?
Galvanic corrosion occurs when two dissimilar metals come into electrical contact through salt water, and that's what manufacturers have to fight. Consequently, they usually use less metal, and what metal they use - stainless steel, aluminum and zinc - is properly balanced for electrical potential.
 
MotorGuide uses a process called aluma-coating that isolates dissimilar  metals, Hodges says. It also employs zinc anodes to draw corrosion away from the other metals.
 
To protect its wireless electronic board and microprocessor, MotorGuide pours potting compound into the housing to protect the components. The control box resides in the mount and the digital module is located in the lower unit. Nothing electronic is housed in the head of the motor.
 
Minn Kota cleans all metal in a multistep process before the parts are anodized with zinc dichromate armor plating. They're then coated with an epoxy primer and finished with a 5 mm thickness of polyester powder-coat  paint. The company also fully encapsulates its control boards in marine-grade urethane and uses heat-shrink tubing to coat connections.
 
Minn Kota also employs a sacrificial anode, which is placed on the hub of the prop.
 
Perhaps the most difficult aspect of protecting a saltwater trolling motor from corrosion, however, comes in keeping the DC motor safe, Brown says. To work properly, the DC motor's rotor and magnets must be housed in a ferrous-metal enclosure, meaning it must contain iron. The DC motor rests in   the center section of the lower unit. "Getting the coating process right is absolutely essential," he says.

What's the best way to maintain a trolling motor?
"Rinse, rinse and rinse some more," Brown says. "I even suggest dunking the SP and ST [Riptide models] in a bucket of fresh water after use to remove sand and debris."
 
Anti-corrosion spray can also help protect the motor, as will touching up any paint nicks in the lower unit with outboard paint. "Remove the prop every few months to ensure there's no fishing line under it that can eat through the motor seal," he says. "Lightly file out any nicks on the leading edge of the prop to reduce noise and cavitation."
 
Clean the entire motor with fresh water after each use, Hodges reiterates. But follow the same practice you use when rinsing fishing tackle: Avoid spraying with excessive water pressure. "And use good electrical grease on any electrical connections."