I pulled the starting battery from my boat last week so I could use it for a portable winch. When putting it back in I screwed up for a second and had the terminals swapped, but never started the engine or even had the key in the switch. Realized my mistake and got things put together right.
Anyway, a few days later, I put the boat in the water to putt around the small lake I live on and play some more with my new toy to figure out it's intricacies .....and the voltage display on my 899 was only 11.8 volts....normally 13.8. HMMMMM....makes me wonder. After a while, and doing all the hard stuff first, I found a blown fuse in the engine...25 AMP. Changed it out and all's good now. I'm taking the boat to a much bigger lake this weekend and I could have ended up with a real pain-in-the-butt situation. (I have two trolling motor batteries, so don't think I would have been stranded, but it would have been embarrassing at best) My boat doesn't have a voltage meter, just Tach, Gas Gauge and useless speedometer. If it wasn't for the Humminbird, I never would have known there was a problem until my engine died or wouldn't start.
The unit sure does come in handy for more than just finding fish!! I've since changed the low voltage alarm to 12.5 instead of 11.5. I get alarms when I trim the engine sometimes, or on engine start-up, but I want a good heads up if something isn't working as normal. It' a nice function that I thought I'd never need.
Now if they could just build in a black-fly and mosquito repellent into the units, it would be even better!!