Black Box Techniques
Chapter II. Factors that Affect Your Boat's Electrical Condition
To take advantage of an electrical charge to catch fish, there are several criteria which must be observed. Even without a Black Box there is "natural" voltage generated on a downrigger wire that can significantly assist the downrigger owner in improving his catch. With or without a Black Box, the following steps should be observed.
1. The downrigger spool and stainless steel cable must be insulated from the boat hull. This allows a natural voltage to be generated on the cable. Most downriggers with plastic spools are insulated by the manufacturer. Some manufacturers intentionally connect the downrigger cable to the boat's electrical system as a means of stopping the retrieve when the downrigger weight breaks the water surface. This does the opposite of what you want. A high voltage is placed on the downrigger wire which repels fish.
2. Check the zinc sacrificial anodes on the boat and on your outboard or outdrive. If they are more than 50% dissolved, they should be replaced. If they have a coating of slime or growth, this should be cleaned off. Use a stainless steel brush or a non-metallic scrubber so that the zinc is not contaminated with a foreign material. New zinc anodes should meet MIL-SPEC MIL-18001. (Zinc, -0.1% cadmium and -.025 aluminum)
3. Bare lead downrigger weights usually produce a harmful charge. Impurities that are present in the lead cause the problem. Scrap lead from auto wheel weights can be particularly bad because it contains antimony (tin). The best practice is to use only coated weights. Vinyl or powder coated weights are readily available on the market, or you can paint or vinyl dip them yourself to insulate them.
A bare lead weight will react with the stainless steel cable and create a problem voltage right in your fishing zone. To be safe, always use coated weights.
4. Do not use a metal snap to connect the downrigger cable to the downrigger weight. Use a nylon snap hook or connect the weight with a short piece of monofilament to insulate the weight from the cable. If the lead weight is hooked directly to the steel downrigger cable, a separate and often harmful electric field will be set up.
5. If your downrigger cable is more than 2 years old and has been operated heavily in saltwater, it may have become etched from galvanic action. This means it has been worn out both electrically and physically and should be replaced.
6. Some fishermen attempt to create the correct voltage by crimping zincs on their downrigger wire or by placing copper or other metals near their lures. This is not advisable. Often, a zone of harmful voltage will be set up somewhere in the system. It's best to keep your cables and weights as "clean" as possible and then get the correct voltage from the Black Box.
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