I have had some sorry experiences with my marine electronics. I kayak & kayak sail on the sea where the water state can be worse than on inland lakes and it is a marine environment so my comments should be qualified with that info. I have used Lowrance & Eagle/Cuda FF/chartplotter units that are supposed to be waterproof and 'kayak- ready'. They have been installed via a ramball mount in the RHS drink holder on my Adventure using a Ram 'stalk' which is abut a hand's span tall - the head unit has then been screwed onto a plastic ram ball base with the cables running through a waterproof seal into the hull where the battery and transducer are located.
Now the problem has been 2 things: one is wave splash over the unit - basically the ramball stalk has not been long enough to lift the electronic device above the wave splash so they have been getting a regular dousing with salt water. I always wash my boat off after use and like to think that I have taken care of the electronics but they have all suffered as a result - typically from corrosion of the connectors and/or water entering the units themselves to the point that they go haywire. The second problem has been the 'waterproofness' of the units themselves... basically they aren't (or haven't been).
Of the two types I have used the Eagle/Cuda 250s (now obsolete) that I have had have been OK but have still only lasted so long. These units have rudimentary in built maps so no card slot, but water has still got into them either through the seals into the body of the unit somehow, or into the electrical connections at the back where the salt water has corroded the plug (not the connectors on the unit so much).
The Lowrance Elite 4 DSI that I paid a whole lotta dough for was absolutely useless and a very expensive mistake. This unit has a card slot and you have to buy a Navionics cart to go into it which ain't cheap. But the problem is that the slot itself is not waterproof - not at all, despite what the manufacturer claims - so water can and does get in and it ruins both the unit and the card. Furthermore the warranty is rubbish - I bought the unit online because they weren't for sale in NZ; when it crapped out after about 5 trips I took it to the local Navionics office for service & they told me that I would have to take it back to the country of purchase to get any warranty - this is for a marine GPS for ********* sake: presumably these can end up anywhere in the world !!! but you have to go back to your starting point to fix it if it goes wrong. Anyway, I whinged (like a good Pom) at the supplier who was very reluctant indeed to accept a return and eventually, after several months, got another unit which lasted exactly 3 trips. The other issue with this unit was that the screen is far to small for my ageing eyes to be able to see the detail on the Navionics chart anyway, especially mounted where it was, relatively low down in the cockpit. Be warned!
So the moral of the story and my advice is:
1. whichever unit you choose make sure your installation allows the head unit to ride above any wave splash and close-enough to your eyeballs to be able to read the detail you are expecting to see (I am about to install another Eagle/Cuda 250s - old stock that I picked up cheaply - and this time I am going to use a Railblaza mount because it is plastic - the aluminium ramball ones corrode in the marine environment - and it has a longer stalk which you can add more sections to so that it really is quite high up. I am also thinking of mounting the head unit inside an upended plastic lunchbox without its lid and one end screwed to the mounting plate to protect the top, sides and rear from water splash and rain.)
2. don't believe them when they tell you the unit is waterproof - it is more likely to be water-resistant for a while. If the head unit is sealed you still have the problem of properly protecting the power plug connections. And DEFINITELY don't believe claims of waterproofness if the device has a card slot - if it has one of those a) it is going to be a lot more expensive to buy and replace when it goes wrong and b) it ain't likely to be anything like waterproof enough for a kayak.
Final point - have tried doing my own aftermarket waterproofing using self-amalgamating tape, waterproof duct tape, Captain Tolley's Creeping Crack Cure, silicon goop, etc. Nothing seems to work. I suspect this is because in our summer weather the devices heat up and cool down during the course of a typical trip. The expansion of air inside the unit will, I believe, cause it to expel air through any tiny gap in the seal and then, when it cools down it will also have the effect of sucking air back in through that tiny gap - if water is present then that will get sucked into the device too as it cools down. My conclusion is that electronics and salt water fundamentally do not mix and the only real way of making electronics last in a marine environment is to encase them in a housing which prevents saltwater getting at them - which is pretty darn difficult on your average kayak, so the only options are not to use electronics or put up with the fact that they are expensive and have a decidedly finite useful life.
Don't get me wrong they are great when they work and I would rather put up with the cost and have a FF/GPS than not. But there are fish-hooks...
Hope this is useful
