Throughthe hull depth transducer

Has anyone installed a through the hull depth transducer. Put one in on our last boat and a much easier installation not having to haul the boat.

Bob

About 8 years ago I installed an Airmar P79 transducer on the hull near the forward head discharge throughhull. In salt water it will read to about 200 feet.

That would be my preferred location but the angle is about 27 degrees and max recommended is 22 degrees.The current transducer, MOOR, is located next to the nav station, about 17 degrees, but I think closer to the front would be better. Although I guess if you are going to run aground that extra 8-10 feet won't make much difference.

Bob

Mounted ours under sole in fwd head.
Solved angle problem by modifying a 4" PVC "cleanout adapter" (around $8 incl. threaded plug at big orange store) as follows:
- Cut non-threaded end of adapter to match angle of hull and bond to hull with generous amount of 4200 (please - not 5200! - you may want to move it someday).
- Give 4200 a couple of days to really cure before going on.
- Drill hole in center of threaded cleanout plug for stem of transducer, pass wire and stem of transducer through hole in cleanout plug, slide transducer mounting nut down wire and loosely thread onto transducer stem.
- Install cleanout plug just barely hand-tight into cleanout adapter and position transducer so proper end faces fwd. (direction may not matter - see sounder instructions), then tighten transducer nut.
- Remove cleanout plug and transducer as one, put a little Vaseline on threads of cleanout adapter, then fill body of cleanout adapter with fresh water.
- Put threaded cleanout plug back on adapter and gently tighten as before (letting excess fresh water spill over as transducer displaces it).
- Note - don't make cleanout plug too tight, it may get stuck - the Vaseline will keep it from leaking and you want to be able to loosen it without jeopardizing the 4200 bond to the hull.

Ours works down to full rated depth of sounder (1500'). If soundings get a little weak or intermittent, may need to replenish level of fresh water inside adapter (we have to do this every couple of years). Did this on two boats - current W42 #195 and previous Brewer 35' double-ender - both work great.

Hope this helps.
Frank
Just Desserts

Frank,

I'm assuming you used a regular through the hull transducer, not the P79 transducer, is that correct? The P79 mounted at 27 degrees throws the beam off somewhat. Using some really rusty trig I calculate that the extra 5 degrees put the center of the beam off by less than six inches at five feet.

Your approach is something to consider,

Bob

Hi Bob,
I ordered my sounder with the traditional bronze transducer meant to be mounted on the outside of the hull - the kind with a threaded bronze stem that would go through a hole in the hull.

Cutting the cleanout adapter at an angle to match the angle of the hull results in the top of the adapter being horizontal. Then mounting the transducer in the top of the adapter orients the transducer beam vertically.

I attached a sketch - hope it comes out - and hope it makes sense. (And now you know why I'm not a professional illustrator...!)
(P.S. - in the sketch the vertical proportion of the cleanout adapter wound up exaggerated - in reality, the transducer is only about 1-1/2" from the hull.)

If you have to use the P79-type transducer and are concerned about not being able to adjust it enough to match the angle of the hull, you could probably just make a tapered block of some dense material (fiberglass might be best to match the acoustic characteristics of the hull layup) to bring it within the adjustment limits of the transducer mount.

Frank