I have used Capn software with the little gps that comes with MS Maps and streets. It is about the size of a scrabble tile.
I was plugging in a hand held garmond but it is nice to have the computer connected to seperate receiver so the hand held can be by the helm.
Also the PC screen is nice because it is big, but bad because sunlight washes it out. Also the PC will probably not like salt spray.
A chart plotter is usually left on but the computer battery will usually last only 2 to 6 hours. It takes a minute or two for the computer to boot up and the gps to get a fix.
I found it a two person job. Someone had to be on the helm and someone on the computer hiding in a quarter berth with the curtains drawn.