I agree with SpareParts. I now have a redundant system after a bad experience. The previous owner had screwed the depth finder into the transom and did not seal the screws in. 2 came out when I was offshore and we took on water fast.

The bilge failed, luckily we had a manual bilge onboard (another suggested accessory). After limping back to shore and fixing it, I sealed the holes and installed a second bilge on a float switch, 2 inches higher than the automatic.

Peace of mind is priceless.