Here is a plug holder that mounts into the Garmin Striker Plus 5/7 and possibly the 9cv sounder mounts. Something that really should be included with the sounder mount. After fishing and wanting to plug up the terminals on the cables, the plugs always seemed to have water in them, and putting them into terminals like that, is just downright sadistic! But I'm not complaining, as Garmin really pack a lot of stuff into the box compared to 'other' sounder companies that I have experienced.
It prints with supports around the seating lip. Use a 'Horizontal Offset from part' at 0.5mm for the easy removal of supports. Make sure to NOT have any supports within the pilot hole! As it will print a bridge over the top of that no problem without supports, and supports up in there would just ruin your day I believe.
The pilot hole is 2mm in diameter. Heat up you screw with a lighter and screw it in. Not too hot or it will melt the PLA away like nothing. I wouldn't try to actually tap it, as PLA tends to end up too lose afterwards.