There's not so much a number of officers as a number of skills to watch out for...
Basically a ship in gunnery-combat modem should have the sailing, defence and gunnery skills at 10, reload time is less important than accuracy though
the special skills are also good, especially the defensive and gunnery skills
for boarding actions you should switch all crew to boatswains, and go for the HTH skill
it's not as important to have the boarding skills, but it does help
also make sure to reduce the enemy crew to below 10 with grapeshot or you'll be outnumbered
www.gamefaqs.com used to have a fairly good faq on this game
