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Replacing stock thru hull depth finder with Hawkeye


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Boat is 2005 Sunscape LSV with stock depth finder.

My stock depth finder was not working and after perusing the Crew, and looking at spending up to $600 replacing transducer and/or depth module without getting it fixed and using up valuable space in the bilge with the "new improved" shoot thru transducer - while leaving the old transducer in place, I decided to go aftermarket. The water temp sensor (part of the speedo wheel) was also not working.

So I bought a Hawkeye on Amazon. Great price and good reviews. Here's how I did the replacement.

1. Test the unit (Hawkeye or other) by hooking up the cables and connecting it to 12 volt power then hang transducer in the water so the bottom is just in the water and clear of dock posts, the hull, etc. The first unit I got did not work so sent it back (free on Amazon Prime) and got another in 2 days. Testing first saved having an idle boat with a hole in the bottom! Second unit worked well.

2. Remove old transducer. This was the hardest part of the process. First get under the boat. I did it on the lift on a calm morning. Use a ruler or whatever to locate the middle of the old transducer, which is recessed and has an epoxy filler to make the hole flush with the hull. Punch that spot and drill a 3/16" hole until you feel the bit stop (about 1/4"). Don't try to drill further. Whatever is in there is very hard. Try to be precise since you only have about 1/8 inch to play with (your new hole is only 1/4 inch larger than the old transducer hole). Place a cross of duct tape over the hole. This is to keep the epoxy in place during the next step. Get in the boat and use channel lock or whatever to remove the nut from the stock transducer. Take it and the rubber washer off. Now carefully bend/rock the transducer fore and aft with the channel lock until it cracks off.

3. Now get back under the boat. Carefully remove the tape by pulling it very close to the hull like you would with decal backing. You want the black epoxy to stay put as you start the new hole. (If the epoxy is loose put the tape back on and put some 5 min. epoxy on the inside of the hole where you broke out the old transducer.) With a 2" sharp (new) wood hole saw start drilling straight onto the hull. (I was using a cordless drill since I was in the water) Drill straight since the Hawkeye transducer is almost an interference fit into the 2" hole. If the hole is not perpendicular with the bottom the transducer will not fit flush and flat on the bottom. The standard "wood" hole saw I used cut surprisingly fast. If you do not have experience with hole saws practice on a piece of 3/4" plywood. An orbital motion with the drill is the best way. Once you're through the hardest part is done! Sand the gel coat around the hole with fine sand paper, clean with some acetone, clean up the interior edge with some course sand paper or stone bit, feed the new transducer cable through, push the transducer in with arrow pointing towards the bow, apply some marine sealant, press in, put the washer and nut on the inside and hand tighten. Keep the arrow pointed to the bow.

4. Cut the cable off the old transducer and tape it to the new cable. Use the old cable to pull the new cable up to the helm. Coil the excess in the space in front of the diver's feet. You might want to pull a small line through at the same time in case you ever want to pull any wires or hoses through that space.

5. I put the gauge in the crescent shaped panel to the left of the speedo. Remove it by removing the nut behind it. Carefully use the same hole saw you used before to drill a 2" hole (positioning is important). You want to maximize the width of the plastic on either side of your hole. Don't drill all the way through. Go a ways and then drill from the other side using the pilot hole as a guide. Go slow so you don't melt the plastic. When through, clean up the hole. Press the crescent back in place and use it as a guide to drill out a 2" hole in the panel behind the crescent.

6. Connect the wires per the instructions. I used the hot and ground from the old depth module. Install the gauge. I found it helpful to remove the harness from the back of the gauge cluster. Your results may vary with hand size and dexterity!

7. Let the sealant cure, and you're ready to go.

I now have accurate depth readings (except when surfing on the port side - turbulance?) and also water and air temp.

Will post pictures next weekend.

Edited by minnmarker
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Great write-up! My depth finder quit as well so this is on the winter project list. How did you make sure you were perpendicular to the hull? Eyeball it and hope?

Practice on plywood. It's a feel thing. You want all the teeth to grab at the same time. If you start straight you'll probably be fine. You could always sand it out later with a barrel sander - but much easier to do it right the first time. Don't try to start on the inside.

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Thanks for taking the time to document this! I have the same issue with my temp gauge not working....quit last summer. The water temp is stuck on 135 or so. My depth gauge is very flaky. Sometimes when I start the boat for the first time it flashes shallow and beeps warning. I can usually cut the power and re-start and it will work fine. Then sometimes while underway it will start reading shallow out of the blue. I have looked at the same unit you installed and am planning on doing the same so your post will be very helpful!

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