CONTINUOUSWAVE

I have received excellent information from this forum on downrigger installation, so thought I would ask about transducer installation for a Raymarine Axiom. My original plan was to have thru hull installed during factory build, but that wasn't feasible due to deadrise, so putting a RV-100 on the transom.

I'm considering mounting a Stern Saver (http://sternsaver.com) so as to avoid drilling holes, and am particularly interested if anyone has long-term experience with them in seawater, as my boat will be kept in the ocean most if not all the time. The epoxy used apparently bonds the polyethylene block permanently.

There are apparently diagrams showing recommended transducer placements for Boston Whalers, but Brunswick couldn't provide, and I haven't been able to find one for 210 Guardian/Montauk. As shown in mock-up, I've tried to position the block to allow vertical adjustment such that none of the transducer extends below the hull, or all of it extends below the hull. The transducer would be about 21" from the starboard side and 24" from the centreline. This is slightly further inboard than recommended in the Dauntless diagram, but any further outboard interferes with the tie-down strap. I realize the transducer is directly over the trailer bunk, but the boat cannot be pulled far enough forward on the trailer to interfere.

I've read the excellent reference posted on this forum by James W. Hebert. He doesn't recommend running the cable through the drain hole, but in my case there will only be one cable and the transducer will be a pain to replace even if it runs over the transom. He also recommends port side mount because it's slightly more immersed, whereas Raymarine recommends starboard side for right-hand prop due to turbulence, and I'm thinking it doesn't really matter in my particular situation.

Cheers,
Peter O.

I don’t like running the cable for the SONAR transducer through the splash well drain. It partially blocks the drain.

With a single engine I would not go so far off center as shown. When the boat is on plane the transducer should still be in clean water, no aeration, or the bottom echo will be lost. If too far out from the keel it may get into airy water when on plane.

A safe method is to test the location by mounting the transducer to 2x4 of wood; clamp the 2x4 to the transom so as to put the transducer in position, then test. Just make sure the clamp is solid so it does not shift when underway at some speed. Hint: drill a hole in the 2x4 at the position of the splash well drain hole and through bolt the 2x4 to another piece of wood. That should make a solid mount for a test run.

I would recommend going lower on the transom but not in line with the strake and not in front of the motor. Maybe move to the left a few inches. I would not recommend going through the splash well drain either to run the cable. One day in heavy seas you will regret it. Going over transom is better, but neither look shipshape. Dilling a hole looks much better. Especially if you can get it the inside of the hole under the splash well. This will look professional.

Drill a hole the size of the plug above the water line in line with and above the transducer and under the splashwell. Apply 5 minute epoxy to the inside of the hole. Pull cable from outside into the boat and fill with 3M 4200 and install stainless steel clam shells on each side. Fill the clam shells with 4200. A video is better than just describing.

Starboard side mount gives you a little more ventilation from the prop than port side. Only in slow speeds
But either side is fine as long as it works at all speeds.

Never have used a stern saver and to me looks like something else to fail. You already have trim tabs drilled into the transom, what is a couple more for a transducer?

Its your boat and do what you feel comfortable with too.
Archie

Concensus is mount deeper than my original photo.

Came across a video showing factory install of same Raymarine transducer on 2019 21' Montauk (redesigned, but probably still very similar to 2018 21' Guardian). It [is] on flat portion of lower strake. Some say avoid strake, some prefer the flat portion. Does anyone have experience with either?

Cheers,
Peter O.

I would not drill another hole through the transom for the wire. Just over and up.

For a clean look, route the cable over to the engine bracket and follow it up and join the steering and other cables, enclose the rigging in rigging hose.
In the photo there are 3 cable anchors. I would not use more that 2. One near the stern saver (highly recommend) and another anchor close to the engine bracket. Use a white wrap on the wire and white anchors to mask the color difference.

When drilling in a new transom, drill oversize, fill with epoxy then tap for the screw. Use sealant (not adhesive) under the screw head.

Generally the advice I have read says the SONAR transducer should not be in line with a strake on the hull bottom.

The cable from the transducer normally will have a molded-on connector that will have a diameter of about 0.75-inch. If you want to make a new hole in the transom for the cable to pass through, the hole will have to be rather large to allow the connector to pass through it. And I would not seal the cable in place with any sort of strong adhesive—you WILL have to remove it at some point, if the transducer gets damaged, fails, or you get a new SONAR.

I would not cut off the connector in order to pass just the cable through a smaller hole. A molded-on connector cannot be reused. You would have to make a splice in the cable to reconnect the original connector.

I think running the cable over the top of the transom is the best solution.