1 - length of 1/4" flat bar (the length will depend on your boat.)
1 - Metal square U type bracket
1 - Small piece of flat bar that you can bend
1 - 6" piece of round steel 1/4" in diameter
1 - bolt
3 - Nuts, bolts, lock, and flat washers.
Measure the back of your boat from the top to the bottom at the back corner. Cut your flat about 6" longer than your measurement. Drill a hole in the top of the flat bar where you will put in a nut, bolt, and washers. This nut and bolt act as a safety stop. Take the square type U bracket, which will be bolted to the top back of your boat. Mark this and drill two holes to mount the bracket, but do not mount the bracket yet. Once you have the location of U bracket, measure the distance from the front of the U bracket to the back of your boat so you have about an inch of clearance past the back of the boat. Using this measurement, cut two pieces of flat bar. These two pieces will be welded to the top and the bottom of the upper part of the U bracket. Once you see the pictures it will be more clear.
Now take a small piece of flat bar and bend it around the main piece of flat bar. This piece should go completely around the main flat bar. On the flat side, drill a hole and tap it to match one of your bolts. This bent piece should allow the main piece of flat bat to slide up and down inside of it. Again see the pictures for clarification. Now take your piece of 1/4" round stock and weld this to the bolt you are going to use. This will make a large wing type bolt to secure the main flat bar.
On the bottom of the main flat bar, mount your transducer bracket, the one that came with the depth finder. Drill a couple of holes and secure the bracket. Your piece is now complete and ready to mount on your boat. Bolt the U bracket to your boat and you are done. You are now able to simply loosen the wing nut and move the flat bar up and out of the way to avoid damage to the transducer.
Now for part two of the project. I leave my boat anchored in the water and do not like to leave my depth finder in the boat, so I needed it to be portable. Here is how I did it.
1 - Piece of 3/4" plywood (size depends on your equipment.)
1 - Length of aluminium 1/2" angle stock
2 - lengths of aluminium flat stock 1/4"
1 - 12 volt atv or lawn tractor battery
1 C Clamp
1 - Aluminium lunch box (optional)
Take the bracket that come with the depth finder to hold the head of the unit and your battery. Place them on the piece of plywood and mark their location. Do not put the battery right on the edge of the plywood as you will need and inch or so to mount the aluminium flat bar to secure the battery. Measure the distance around the battery (all four sides) and cut your aluminium angle to the that length. You now have to bend the aluminium angle into a rectangle to fit around the battery. You will have to notch out the aluminium angle at each corner to form the rectangle. Once you have made this test fit the battery for a snug, but not tight fit. Once you are satisfied with the fit, drill holes in the bottom of the aluminium angle and secure it to the plywood with wood screws. Secure the head bracket as well.
Now take the aluminium flat bar, measure the distance over the battery, up, over and down. Add an inch or so to this measurement and cut the aluminium flat bar to this length. You will need two of them. At each end of the flat bar drill a hole. Now bend the flat bar to form a large U type bracket that will fit over top of your battery. Place the battery into the aluminium saddle you made earlier. Fit the two aluminium U type straps over the battery, making sure to leave the battery posts unobstructed. Screw down the strapping on each side to hold the battery in. Your portable depth finder is now complete. You simply clamp this to the boat seat and your ready to go.
See the pictures for details.
Now where does the aluminium lunch box come in, you ask. I got one at a second hand store and it works perfectly for holding all of the parts of my depth finder and provides great protection for the unit.
Hope you like this project and it shouldn't take you more than a couple hours to build at a very minimal cost.