This type of connector has external pins and internal tubes/barrels. By that I mean there are pins that the power plug connects to, and little tubes that the internal wires are inserted into and then soldered into place.
To remove them, its necessary to heat the tube/solder joint while putting gentle pressure pulling the wire from the plug. In this case Garmin has used some pretty beefy wires (12 awg) to go from this connector to the board.
I had initially thought that simply using the solder wick would be the best to remove the wires, but rethought it - the wick is a good gentle solution and really minimizes the heat transfer to delicate parts AND gets old solder out of the way. In this case I was trying to remove beefy wires with a lot of solder down in the tubes of the connecter. I just used a high heat setting, and actually ADDED a little fresh solder to help with heat transfer. It worked really well. I did use a little of the solder wick to see if I could clean up/prep the wire ends to resolder them, but decided just to cut the wire back, strip, and tin new ends. There was enough wire available for this - I only actually cut just under 1/4" off the ends.
I discovered the part I bought was just a hair too small for the wire.
I took a close look at whether I needed to stop and resource. The Garmin draws 4 amps, and my internal power wires from the plug to the board are 12 awg (measured approx .080). This MFD is mounted on the flybridge and gets its power from a circuit breaker mounted in the overhead right above the lower helm station. Its an approximate 10-12 ft wiring run from the breaker to the MFD, which puts me at a required 16 awg for up to 5 amps at 15 feet. I decided to see what size the wire would have to be to reliably get it inside the tubes; I ended up trimming about 8-10 strands from each wire. Afterwards they measured .070 to .071 and fit the tubes of the connector just fine. There was no part number/marking on the connector, I'm thinking that its a like/same but is made for metric wire - 2.5 mm2 wire is supposed to be .70ish. In the end I decided to stick with my trimmed wires due to them still be so far oversized. I tinned the ends of the wires with solder.
I didn't take a photo, but before desoldering I marked the old connector with a + and - where the respective wires were. The connectors did not have a common reference on the back for polarity, the only thing to rely on was the detent on the recess where the plug goes into the connector.
I turned the connector over to identify where the positive is in relation to the detent mark.
Then started off in the same position with the new part...
...and marked the new part the same way. (I double checked this like 10 times!)
Soldering was quick and easy - using my alligator clip stand to hold the wires, I put the connector on the wires and applied solder. (This process was probably 15-20 seconds total and was almost a letdown after tediously cutting out a few strands at a time to get the wires trimmed down!)
A little hot air and the heat shrink was done!
I was able to reuse the black zip tie to hold the noise suppressor back in the same position on the board. They had left enough of an ear I got ahold of it with needle nose pliers and got another 1 or 2 clicks on it and made sure it was snug.
The case has a recess for the oring to seal into - much easier to put the oring around the connector first to assemble.
This ended up being a two handed operation - one hand feeding the connector through, the other pulling it through. Once I had it through I need to keep a hand on the back so it wouldn't pull back out of the hole while I put the retaining nut on.