Do it Yourself Jack Plates

A jack plate is a two-piece metallic assembly that provides on-the-fly height adjustment of an outboard motor. How high an outboard rides in the water determines performance, drag, fuel economy and smoothness of ride. All modern outboards have on-board adjustments to the angle and degree with which the propellers bite the water. None, however, have the capability of altering their vertical positioning while attached to the transom. A jack plate provides just such a capability. Pricey hydraulic models are available commercially, but a mechanical DIY jack plate works equally well and is very inexpensive to build.

Things You'll Need

  • 1/2-by-4-by-10-inch aluminum 90-degree angles, 2
  • Tape measure
  • Permanent marker
  • Power drill
  • Reciprocating saw
  • Compass saw
  • 1/2-by-1 1/2-inch stainless steel carriage bolts, 6
  • 1/2-inch wrench
  • Rented outboard motor hoist
  • Cordless screwdriver
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Instructions

    • 1

      Drill two 1/2-inch holes in one flange of both pieces of angle aluminum. The first hole should be flange-centered 3 inches down from the top edge. The second hole should be 4 inches directly below that hole.

    • 2

      Cut a 5/8-by-6-inch channel in the undrilled flange of one of the pieces. The channel should be centered in the flange, with one end 2 inches from the top and the other end 2 inches from the bottom. Measure it with a T-square and mark it with a permanent marker. Drill a 1/2-inch hole in this marked rectangle, insert the tip of the reciprocating saw and make the long cuts. Use a compass saw to make the corner cuts and clean up the channel.

    • 3

      Drill two 1/2-inch holes in the undrilled flange of the other piece of aluminum. Make the holes flange-centered, 4 inches apart with the first hole 2 inches down from the top. These holes secure the locking bolts that hold the two mounted flanges together.

    • 4

      Connect the outboard motor to the lashing on the hoist. Loosen or remove all connections on the outboard motor-board and lift it away from the boat's transom.

    • 5

      Drill two equally spaced receiving holes in the outboard's motor-board and two in the boat's transom. Bolt the jack plate angles to the transom and motor-board tightly with 1/2-by-1 1/2-inch stainless steel carriage bolts. The piece of angle that attaches to the motor-board is the piece with the channel. It is the other flange that is bolted to the motor-board. The corresponding flange (with matching holes) on the other piece is bolted to the transom. Seen vertically, the two pieces of the jack plate form a connected channel.

    • 6

      Move the hoist into position and connect the two pieces of the jack plate with two 1/2-by-1 1/2-inch stainless steel carriage bolts. The nuts should be on the outside of the assembly for easy access.

    • 7

      Launch the boat and loosen the carriage bolts with a cordless screwdriver. This allows the motor to float up or be pushed down to the correct height. Spin tight the locking nuts on the jack plate and power up.