Fish finder, water inside, drill holes or not?

[vpt]

So here is the story. I have this boat, set up for a eagle fish finder which we got new back in like 1992. After being left outside for awhile the fish finder got water in it and the screen started dropping lines of LCD's or whatever they are. I then drilled two holes in the bottom oft he fish finder, drained the water, and the fish finder worked for a few years or so like it was with a few lines of lcd's missing. After awhile we found someone selling the same fish finder and bought it as a spare. Well eventually the original dropped line after line till it was unreadable and I pulled out the spare (new/used) unit. The new one worked good for a few years and then the same scenario went down. So here we are today with a near dead second fish finder and once again I purchased a third unit in like new condition off ebay for $15 ready to go on and be used.

Now my question is, should I drill the holes in the bottom of the unit ahead of time? That way what water gets in drains out right away and there would be no build up till eventual unit death. But would it also create condensation in the unit? These are supposed to be complete sealed units and were either considered water resistant or proof when new. It is just over a few years the water finds a way in somewhere. In the last two units they seemed to be "ok" after I drill the holes in them for at least a year or two but then eventually enough lines go blank that you can't read the display. I am thinking once the water gets to the electrical the first time the corrosion is already set in and it is just a matter of time before everything just corrodes and quits. I am thinking preemptively drilling the holes will keep enough water out to avoid the corrosion. But I worry about rainy days and humidity getting up threw the holes as well and destroying the unit that way.

What to do? The boat and fish finder sit outside all summer in the rain and all, winter the boat is stored inside. I never have to touch any buttons besides the power button so thought maybe I can coat the entire things with something to keep the water out or put a bag over it or something?


I don't want to have to take it off every time I leave or use the boat.

[Cuttings]

Andy
Here is how I see it. First we are not sure whether the moisture is condensation or water leaking in from rain.
One of the problems with these so called sealed units is it will build up internal pressure when it gets warm in the sun and possibly push air past the seals.
Then when it cools off and rains there is a negative pressure inside which can draw the water in.
A cover may be all that is needed, but you could drill the holes and put screws in to seal the holes up again.
You could then remove the screws once in a while during dry weather to check for moisture
I think I would still cover it up in any case, but leave the cover open at the bottom so you don't build up humidity inside the cover..

[RichR]

Hi Andy
We have a GPS that we use on my friends sailboat. When we are sailing it's mounted to the outside of the cabin. When we tie up, we leave it inside the cabin.
The unit is well over 10 years old and has never had a problem. It sounds like you are leaving it exposed to the elements. If so, covering it up may help.

[achtanelion]

I'd probably see where I could stick a small clear (glass?) jar of desiccant on the case. Fortunately, you have 2 dead units to experiment on. If you have a wife, one of her little jars of potions and lotions might be ideal. The case of the fish finder is probably ABS, so a jar with a compatible lid wou let you glue it on. Once you have your materials, I'd:

Drill out the jar lid and install a screen.
Bore the case of the fish finder to a tight slip fit on the outside of the jar lid.
Glue them together.
Install desiccant.
Change it when it goes pink.

Bulk desiccant can be got at craft stores for drying flowers.

[vpt]

I'd probably see where I could stick a small clear (glass?) jar of desiccant on the case. Fortunately, you have 2 dead units to experiment on. If you have a wife, one of her little jars of potions and lotions might be ideal. The case of the fish finder is probably ABS, so a jar with a compatible lid wou let you glue it on. Once you have your materials, I'd:

Drill out the jar lid and install a screen.
Bore the case of the fish finder to a tight slip fit on the outside of the jar lid.
Glue them together.
Install desiccant.
Change it when it goes pink.

Bulk desiccant can be got at craft stores for drying flowers.

I like this idea. Only problem I will have to look over is there isn't much room under the unit for even a small bottle but I have to look at it again. There may be room off the the side or something.

How about a tube? Could a hole be drilled in the unit and then a tube plumbed from the unit to the desiccant?

[achtanelion]

Well, if you were going to use a tube, a couple holes in the side and a tube mounted like a sight glass might look pretty cool.

[Black_Moons]

If the unit is sealed, a tube would work as it would let the air pressure equalize and only allow dry air in.. but I think you would be better off with a more direct connection. What about something like a 1/2" deep tray under the unit, filled with desiccant.

Glue the 'lid' of it to the unit somehow, it does not need to be air tight, just designed in such a way that any rain/splash water won't get in easily.

[mike anderson]

How about a gallon freezer bag and use a small bungee cord to keep it in place. That will keep the water out.

[vpt]

How about a gallon freezer bag and use a small bungee cord to keep it in place. That will keep the water out.

That is one kind of thing I was thinking could work. Thats also why I mentioned some sort of clear spray on film (clear coat/acrylic) or a lay on clear cover like clear tape. It is "like a bag" just better fitting.

What about that pourable self leveling acrylic you see some places like bars cover wood tables with?

[vpt]

This is the unit in question without the big box it sits on.

[Black_Moons]

How about a gallon freezer bag and use a small bungee cord to keep it in place. That will keep the water out.

Hmm, Maybe he could put desiccant in the bag, seal the unit in there (disconnect it from wires?) when in storage, then remove from bag and use as normal when using the boat?

Kept in a 0% humidity environment in storage, as it slowly vents in/out with temperature change, the moisture will get sucked out instead of getting in.

[vpt]

Hmm, Maybe he could put desiccant in the bag, seal the unit in there (disconnect it from wires?) when in storage, then remove from bag and use as normal when using the boat?

Kept in a 0% humidity environment in storage, as it slowly vents in/out with temperature change, the moisture will get sucked out instead of getting in.

With the venting out and in with temp changes, couldn't a remote canister with the desiccant be used with a small line like a brake line (fish aquarium hose) be plumbed to the unit and work sort of the same way? Expel air and moister when heated and draw back dry air when cooling. But then also at that point why not two lines to have a possible circular air flow path?

[Black_Moons]

With the venting out and in with temp changes, couldn't a remote canister with the desiccant be used with a small line like a brake line (fish aquarium hose) be plumbed to the unit and work sort of the same way? Expel air and moister when heated and draw back dry air when cooling. But then also at that point why not two lines to have a possible circular air flow path?

Sure, if you either A: Pump air through the system, or B: Know the unit is 100% sealed and that air will only flow through your hoses and not take the shorter route through the case.

My idea also does not change the unit, just how you store it when its not being used.

[achtanelion]

Can you open up one of the dead units and take some pictures so we can see where something might fit?

[vpt]

Can you open up one of the dead units and take some pictures so we can see where something might fit?

I have destroyed the first unit opening it up to see whats going on. I did have it on my bench for a year after that before throwing it away. I can also destroy this second unit now that it doesn't work to open it up. There is no "taking it apart" it is sealed together with an epoxy or something like it. In fact it seems as though the screen and board were layed in a mold and the plastic was poured or injected around it.

There is only two little spots where I could get a drill in to a very small air pocket that would let the water inside out. I will cut open the second unit for pictures and whatnot though.