I use the Electro-Steer many hours at a time, several days a week.
I bought the '101' salt water model. My boat is moored in salt water 6 months every year. The Electro-Steer is mounted on the transom fully exposed to the elements including rain, salt spray and even occasional raw salt water.
Within a few months of my initial install I had to return the unit for service. One day it stopped working with a very hot motor, but it seemed to recover when it cooled down. The next day it quit after less than an hour, also very hot. At that point I returned it for repair but Marine Tech took awhile to fix it and I'd put the boat up for the winter before I got the Electro-Steer back. I've no idea what they did to fix it.
The next spring when I started using it again it worked fine for about a month then the same symptoms came back. It was no longer in warrantee, and, thinking the electric motor was the problem I ordered a new one. But it was not until a couple of weeks later when the motor arrived and I went to install it that I found the real problem.
I disassembled, cleaned and greased the machine and was reassembling it with the new motor when I noticed the slide was still extremely difficult to move. I discovered that the slide is two pieces: a thick bottom slab of steel and a thin top slab of plastic. The plastic slab was wider than the steel, and it was jamming in the slot the slide was supposed to move in. I trimmed the plastic back to the steel (1/32" to 1/16") and - no more problem. I put the original motor back in and all was well.
I've gotten in the habit of so 'servicing' the Electro-Steer every year in the fall when I put the boat up for the winter.
Why is this necessary? I think corrosion builds up between the slide's steel slab and the plastic slab, and this corrosion causes the plastic to be compressed between the steel slab and the top of the slot the slide moves in. This compression causes the plastic to 'pancake' - expand in the only direction it can - outward. When the plastic expands far enough it presses against the side of the slot, creating friction that causes the motor to overheat and stop working. Just my theory...
That's the only problem I've had with the Electro-Steer in several years of hard use.
Update: Turns out that expanding outward, while mostly side-to-side, is also end-to-end. After a couple years of this it got to the point where the holes in the plastic didn't match the holes in the steel plate, so the plastic buckled between the screws! I suppose I could have figured out a way to fix this, but instead I just ordered a new plastic slab ($18 part).