A question for those who have used hole saws-was it on newer boats?
My boat is a '74 and the gelcoat will chip from a drill bit with light pressure. I wonder if the age has something to do with it.
I've always used a Rotozip, or spiral saw, for these kind of jobs. It cuts with what looks like a drill bit but is actually a cutting blade. This offers a very smooth method of cutting fiberglass, without all the bouncing around that a skillsaw or jigsaw can cause. I cut a 6" port in my '72 Fish last year, and the result was great--no chipped gelcoat, etc. It took a total of 30 seconds or so. You just have to work carefully since the Rotozip really does cut through fiberglass like the proverbial knife through butter!
I should add that these kind of saws are available at many places and by different names. Harbor Freight (if you have one around) has one pretty cheap:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42831