taking care of fish finders in saltwater.

my Garmin is supposedly water proof/resistant.  I rinsed it at home under a gentle stream.   I did coat the electrical connectors with di-electric grease.  at home, I wiped them clean, and I blasted them with contact cleaner. 

I helped a friend remove and replace a fish finder that got crusty from salt exposure.  the prongs snapped off within the unit.  trying to avoid all that.

I jet blasted my pedal drive as well, and I plan on greasing it after my coffee this morning. 

rust is inevitable?

Yeah, they wont last forever but you can do some preventive maintenance like you are doing.  My last head unit the power button stopped working. after 1.5 years.  Never dunked, but splashed while sailing on occasion.  Rinsed and dried after each session.  Pins were good with the dialectric grease, that is #1 on keeping the positive pin from disintegrating. One other tip Bushy gave was to give a light coating of WD40 on the head unit and wipe it off, like adding some water resistance to the unit overall.

I have a Garmin FF and I'm a big fan.

I rinse my FF and connector cables with fresh water after each use. Other than that, I put dielectric grease on the contacts less than once per year. My current unit is just a few years old, but I had one previously that lasted forever (like almost 10 years). Given how flimsy the pins seem, in my experience at least, they actually hold up remarkable well. My FF gets splashed constantly when sailing my AI and/or in rough conditions.

In the picture, you can see a little crud on the power connector, but it does not affect performance.

I have the Garmin Striker 4, and my only real complaint is the cable and connections. Teeny tiny wires for the power, teeny tiny pins on the connectors, and no locking mechanism to keep it all buttoned up together. Not much room for corrosion there before things don't work.

Of course, as mentioned, dielectric grease goes a long way to protecting the cable ends and connectors. WD 40 is a good idea to help protect the plastics.

In the picture, you can see a little crud on the power connector, but it does not affect performance.

Mine is about 4 years old, and my cable ends are in about the same condition as yours.

…and no locking mechanism to keep it all buttoned up together.

It’s true that there is no locking mechanism, but they fit snuggly and I’ve never had an auto-disconnect. Maybe my lack of dielectric grease is the key…

…and no locking mechanism to keep it all buttoned up together.

It’s true that there is no locking mechanism, but they fit snuggly and I’ve never had an auto-disconnect. Maybe my lack of dielectric grease is the key…

I put too much grease in at first, and they would pop off if I so much as looked at them, haha.  I cleaned a little out and haven't had that problem since.  Your connectors look pretty good for no grease!