Do you have one of the Harbor Master Marinettes from the early to mid 90's? I think someone else with a 1994 model said only the hull was Aluminum.
I can say on the 1980's on back to the very beginning were all Aluminum. Lots of fairing compound and jigs were used to bend and form the traditional Marinette design.
There is a very small amount of fiberglass in many original Marinettes. Anyone guess where that fiberglass is located??

Hint: Its "in" the hull.
-Karl
1986, 32' Sedan, twin 360ci, 275hp Chrysler's w/ K&N flame arrestors