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Downrigger Structural Designs
A right-angle side mount downrigger clamps down directly over the side rail, using compression screws. A pedestal swivel mount-type downrigger bolts directly through the top side rail, or over the top of the transom rail, using steel through-bolts. Rail-mount downriggers, used on the side, or transom, rails, clamp down over the rail with compression screws. A pedestal riser downrigger mounts with through-bolts on the side rail or transom top, and comes with a vertical extension shaft for lowering or raising the boom. A gimbal mount downrigger bolts directly to the gimbal housing.
Downrigger Types -- Boom Length
Boats with a length of 15 feet or shorter do best with short-arm booms of 20 to 40 inches. Boats with lengths of 21 feet or more do best with long-arm booms of heavier construction in lengths of 30 to 48 inches. Boats in between the sizes of 16 to 21 feet can use either short- or long-arm booms, as long as enough boom clearance is provided to avoid tangling during heavy seas or sharp turns. If swivel plates are not provided in the kit, the owner is best served by purchasing one that fits his downrigger model. Swivel plates allow rotational movement of the boom, for clearance purposes.
Manual vs Electric Downriggers
Manual downriggers have cranking devices to lower and retrieve cable. They can come in several designs and types but work best on smaller boats, where seating next to the downrigger is provided. Electric downriggers also come in the different types and designs but need at least 12-gauge wire for lengths up to 25 feet of wire, hooked up to the battery. Using more than 25 feet of electrical wire requires the downrigger motors to have 10-gauge wire. Electrical downriggers need a 30-amp fuse spliced into the positive battery wire, located at least a foot from the positive battery post.
Dual Setup Mounting Location Methods
The preference of the boat owner determines the amount of downriggers and their locations. Two stern-mounted downriggers, located at the ends of each transom corner, provide a practical, simple choice. The booms should be long enough so the cable does not trail near swim steps or engine props. The most common mounting method keeps the booms straight off the stern, perpendicular to each other. This allows the cable to trail directly behind in straight, even lines. Clamp-on downriggers go in the same location, provided the transom is thin enough to allow their installation.
Multiple Downrigger Location Methods
A boat owner can install four, six or more downriggers on his boat. Location and convenience is key. A popular four-mount setup requires two downriggers bolted to each rear end of the transom corners and two downriggers mounted 1 foot aft of the stern on the gunnel rails. A six-mount setup would have four downriggers mounted on the gunnel rails, spaced 1 foot apart from each other, and two on the transom. The transom could receive four downriggers, provided the transom is wide enough to keep the inboard downriggers far enough away from the prop location. Balance is important, spacing all the downriggers in evenly spaced locations.
Securing Methods
Most downrigger mounting plates have four bracket holes that through-bolt into the gunnel rail or transom top. The rail and transom must be wide enough to accept the plate dimensions. The underside of the downrigger mounting plate should not interfere with steering cables, wiring harness, brackets or any obstructions. Stainless steel bolts, spacers and lock washers should be used as securing hardware. For very narrow side gunnels and transoms, clamp-on downriggers provide the best securing method. If the transom or side gunnels have thin construction, it is necessary to bolt on an extra plate or reinforced gunnel or transom board, to stabilize and strengthen the mounting surface.