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In-hull mounting - Airmar P79 transducer

Emerald

Moderator
Hi All,

I'm looking at adding fish finder/bottom contour information to my GPS - I'm really after bottom composition and contour more than fish, and this requires addition of a 50/200Khz transducer. There are many flavors available, and the one Garmin has for in-hull use e.g. don't cut a hole but shoot through the laminate is an Airmar P79, as seen here:

http://airmartechnology.com/airmar2005/ex20/RMProducts/ElectCat.asp?ProdID=52&Man=Garmin&PageNo=99

Here's my big question. I used one of the P79s with a simple depth finder many years ago on my prior E-27, and it worked. This was not using it as a transducer for fish finder/bottom contour information. I am trying to figure out if there is a sensitivity difference that might come into play between how the signals are interpreted. Also, the Indpendence 31 is about 1" solid layup on center line, and is going to probably be in the 3/4"+ thick range down in the bilge area where I would mount this. I believe this is thicker than my E-27 was. Does anyone have real life experience of using one of these as a fish finder/bottom contour instrument and did it give consistant readings?

Thanks in advance for any and all feedback.
 
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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
The Duck comes down with the Sign

Absolutely Amazing. You asked about the exact Garmin depth sounder option (for my 3005C) that I bought... for about $250. The good news is that it works fine at reading thru the hull on our boat. FWIW our hull is probably about a half inch thick in the aft part of the bilge where I located this transducer. Probably just me, but it took me ages to figure out how to rotate the base just right before using sealant to bond it to the hull. I filled it with a water/antifreeze solution and it worked immediately.
:rolleyes:
There is, however, some bad news. The top of the unit with the actual transducer uses a bayonet lock concept to mate it to the base. The plastic molding is only about a sixteenth inch thick that locks the tabs into place. Within a month of usage the plastic broke off on the little cast groove on one side and enough liquid leaked out to put an air bubble under the transducer and stop readings. With some effort and string and a MacGyver version of tying down the top it worked again. Poor design by AirMar, imho. :mad:

Next all signal was lost... and I found that the plastic plug that locks the pin connection into the Garmin black box had vibrated enough to break one side of it's little plastic securing tab. More string. Some swearing.

This month the signal started going away again, off and on depth numbers, which indicates that the fluid has seeped out too much.
This bit of kit is, by far, the worst-engineered and built marine item I have ever seen. After the famous Garmin date snafu this last August, I only wish I had spent a few more $$ and gone with the more "commercial quality" Furuno plotter/sounder combo.

Sorry to retreat from my usual cheerful demeanor, but this Garmin thing really irked me. All this happened out of warranty, of course.
One minor lesson: Always install this stuff immediately after you buy it! Do not delay. :mad:

I have, in a past life, glued a transducer to a bilge surface with sealant, and it worked just fine. It did, however, reduce the signal return range from an advertised 400 feet to under 200.

Regards,
Loren
 
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Emerald

Moderator
Hi Loren,

great insight - this is exactly the type of feedback I was looking for. Sounds like I need to make sure this thing is installed with major strain relief on all fittings, connections etc. How disappointing to hear, but good to know up front.

Keep the reports coming in. This is all helpful information.

Thanks!
 
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