Can someone please tell me what battery is #1 on the battery switch of a 2008 23 sport? Port or starboard
Assuming that you are referring the the battery selector switch (Perko switch or equivalent -- that hat positions #1, #1, and both), and that you have only one switch, put it on the #1 position, and see which engine cranks. Another way of telling is to disconnect the + cable on one battery, put the switch(es) on #1 position, and see if the port engine cranks. If it does, then #1 is port. Same test for #2 position of switch.