Have the same thing...
Connect 182 NMEA output (blue wire, I think - check the book)to the ST4000 NMEA input (+).Besides the 182 red wire for power, connect the 182 ground (black wire) and a wire from the ST4000 NMEA (-) to a common ground - I used a terminal strip.Go into the 182 setup menu - you need to change the default setting from Garmin - Garmin to NMEA In, NMEA Out. That's it. If your speed/depth/AP are on the Seatalk network, you can also display SOG from the GPS on the knot meter, as well as BTW, XTE, and I think DTW on the autopilot.You need very small female quick-disconnect crimp-on connectors for the NMEA pins on the back of the ST4000. Radio Shack has them. The smallest they have is 22 ga. 3/16 inch, which will work. Ideally, I think 24 ga. 1/8 inch would be better, but RS doesn't carry them.