Near dead FF repair: Sometimes magic

  I was a little careless with the head of my Pirranha 4 fishfinder - it got bounced in a pack and got wet on a wet launch and landing, got it home, and after it dried off, I plugged it in.  It would turn on as soon as I plugged it in,without hitting the "on" button,  and it erroneously said the transducer was connected, but wouldn't work otherwise except to beep.   It would turn off, but not back on with the power button, had to replug the power cable.   Clearly, it's brain was confused.  After trying everything I could think of, I sucked it up and opened it up- it takes a special screwdriver- Torx.  I didn't understand what I was looking at except the tiny drops of water on the inside. I dried up what I could see, and put it on the shelf, open, for a couple of days, then closed it back up and tried it.  To my amazement, it WORKED! 
     I don't know how the water got inside, I kind of think it got in thru the connection sockets, so I cleaned those good and put tons of light bulb grease in them.  The power cable sometimes will wiggle and break the contact, so I think something's loose in there, but that has been going on for months- it seems to work fine once I get out on the water (and wet?).   
   There is a small piece of tape on the bottom where a serial number might have been, you take it off and there's a slot to pry the halves of the case apart.
It lost it's stickum, so I replaced it with vinyl tape and for good measure taped over the rubber seal between the 2 halves around the outside and over the scews I had replaced.  Took it out today and it survived one trip.  I'm going to make something to protect the power and transducer plugs from getting hit when plugged in- by stuff like sinkers, nets, etc.   I feel like I won a small repair lotto!
   

Tom, welcome to world of Piranha FF owners.
I've experienced everything you have and much, much more.  I own two and both have been back to Humminbird at least once, and I even resuscitated both back to life several times on my own.  Moisture is the most common problem.  Even though the heads have nice silicone seals, water still gets in somehow.  Secondly, the connectors are very sensitive to corrosion, so silicone dielectric gel is a must.

The only reasons why I endure the torture is that both of my units have portable bases (Piranha 1, Piranha Max 10)... which, IMHO, are still the best designed portables on the market.  Also, Piranhas cost nearly half as much as many other FF's.

Since my hull mounted and suction cup transducers are interchangeable, I doubt, I'll buy a different FF until both heads crap out.

Chuck do you use the stock battery set-up? Waterproof?

Mike, I use and really like the stock battery setup (8 AA's) on the portables.  With standard alkalines, I can go up to 6 full days of fishing before replacing.  With 1800mAh rechargeables I can go about 4 full days before recharging.

As for being waterproof, the seals work great.  I've only experience moisture in the battery case once, and that was my fault for not tightening the screws down enough.

The Piranhamax family is a great little FF.  If you can get 2 seasons out of one, you should be happy.