View Full Version : Depth Transducer Location?

Blind Horse
01-06-2014, 06:40 PM
Where is the depth transducer typically mounted on 18 classics out of the factory?

The transducer that came on my boat is not epoxied to the bilge, just hanging there. Its a Gaffrig 5001 series with flat puck (not angled puck). I wonder if maybe it isn't the original one since I would expect to see an angled puck transducer or some sort of angled shim to generally match the hull deadrise. My transducer doesn't seem to read through the flat keel area along the bilge centerline when I fill the bilge with water and set the transducer on the keel, maybe the boat is too thick there or the transducer is weak. I would like to know what others have done.

Jeff Vander Yacht
2001 Classic 18 - 383 Scorpion
Bellingham, Washington

01-06-2014, 07:38 PM
A big dollop of RTV silicone sealer on the bottom of the puck works very well. Just wiggle it a bit when putting it into place to expel any air. It won't fracture like epoxy often does.
Of course, if it is original, it may not be working anymore.

01-06-2014, 08:34 PM
Would not be surprised if it's too thick at the keel. Lots of useful info in the attached link that's probably applicable beyond this particular model. ( I have one and installation was easy.)


01-06-2014, 09:49 PM
George, What transducer are you using and where is it mounted. Also, not to steal the thread but I have been following your complete over the top restoration of your boat and was wondering what make horn are you using? I see it mounted through the hull in a picture.

01-07-2014, 08:27 AM
As George mentioned RTV works very well, the puck does not have to be mounted by the keel very few are. A transducer puts out a cone shaped signal it will read bottom even at more than our 22 degree dead rise. Years back I tried to duplicate a basdic sonar a Swedish invention to see 360 degrees around the vessel. I mounted a transducer horizontally on a pole, I went to test it no mater which way I turned it it read bottom. I was surprised, try it for your self before you mount one hold it over the side and turn in all directions watching the scope.

01-07-2014, 10:31 AM
From my research (not testing, just reading and some conversation with AirMar folks) beam cone angles vary. And even so, I suppose it is possible at shallow depths one might see wrongly-aimed beams still providing useful returns, where they would not do so in deeper water. (Which, if true, might be okay since most of us are not fishing and are primarily concerned with not going aground.)

i believe the instructions I linked give a range of acceptable thicknesses for the glass at the mount point (for one model), as well as explaining that the transducer won't perform when shooting through coring. Also, if one has a single prop, avoid mounting on the side of the boat where the blades are coming up toward the surface, doe to compression waves coming off the prop.

Best advice is probably what was mentioned earlier about testing until you find a location that works.