Tuesday, August 12, 2014

P79 transducer install and repair

I've given some thought to what color this slightly lubricious material is and I have two options. The first is petri dish pink. The second is hot porno pink. You know I choose the more salacious name for this not occurring in nature color. This is the back end of a Airmar P79 inhull transducer installation repair. The housing apparently is leaking ergo it's my fault since I installed it. The porno pink colored stuff is nontoxic antifreeze, aka propylene glycol.

Installation of the P79 inhull transducer is straightforward but long term success depends on making sure there are no leaks. This can be difficult to determine at the time you install it.

I have only had a couple of leakers through the years and they have been slow ones. These can mostly be attributed to the sometimes god awful awkward places they end up in. Outboard of a stringer, under a V=drive, in a unlit dirty oil coated 120 degree engine room.

Installation of the P79 transducer is simple, if you read the directions first. Clean the space thoroughly with the stuff of your choice. Sand the area until it's generally level and then give it a final wipe down with a solvent like alcohol or acetone to insure it's completely oil and grease free.

The base has to be glued to the hull, and my first and only preference is quick set Marine-Tex epoxy. I abrade the transducer flange to insure adhesion, and wait a minute. Ding Ding Ding. It's time for an "Installers Tip".

The transducer housing is black, engine rooms aren't famous for good lighting, and the transducer base has a specific orientation. So to reduce the chances of a screw up I put a piece of blue tape on the keel side of the base so I don't screw up. Apply the epoxy and stick it in the right place. Hold it for about a minute so it won't slide downhill out of place. 

Back to the leak. It was tiny, slow, but still had to be fixed. In days past I used mineral oil. This involved going to my local drug store, locating the laxative section and it's always there on a bottom shelf.

I would take it up to the crusty old cashier, and endure her knowing smirk. I know what she's thinking, "If you're that sick you oughta see the doctor." Now I use the porno pink non=toxic antifreeze.

In this case I had used the mineral oil. Step one, use paper towels to soak the stuff up. Step two, take some sort of cleaner and do a good job of cleaning the inside of the housing. Step three, wipe the interior with alcohol. This is not a good place for acetone unless you want to melt the housing.

The fix to to take some 5 minute epoxy and seal the housing from the inside. The thing to keep in mind is to keep the exposed hull inside the housing clean. This is the acoustic window.

If soft materials like five minute epoxy, silicone or other sealants end up on the window it will dampen the sound waves degrading performance.

The remaining task isn't daunting. Mix up some cheap epoxy. Extend the digit of your choice, scoop up some gloop with it and apply it to the inside seam. Try to not get it on the window. If you do just take a paper towel dampened with some alcohol and carefully wipe it off.

Wait the five minutes for the epoxy to kick.  Add the porno pink liquid, and put the transducer back in place. Clean up and wait a few minutes to check for leaks.

The pluses of the pink antifreeze are over the long run it's cheaper, unlike the clear mineral oil it's easier to tell if some is leaking out albeit even slowly, and no one is going to give you a knowing smirk when you buy it. Elapsed time about 30 minutes, and this was a no charge. But if someone else had caused the problem.....


  1. Close Bill, but that color is Hooker Pink, lipstick that color is more visible in the dark...

  2. I believe that some antifreeze also has a dye that will fluoresce under UV light to aid in locating leaks.

  3. I'm losing readings past 15 fathom...could this be a leaky housing issue?


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