I chartered a 331 many times; that screeching hatch would drive me crazy! Its a characteristic of that vintage and model.
I would suggest that you remove the fiberglass sea hood that will allow the removal of the acrylic slider lens. Clean the lens thoroughly as well as the rub rails and seals. Spray some Sail Kote on the seals and slider. Hopefully that will help. Also check that the fiberglass seahood isn't rubbing on the acrylic lens. Happened on my 343 and scratched the lens and screetched as well. Had to sand down the seahood to eliminate the rubbing. I have read where individuals have trimmed the rubber seals on the 331 to eliminate the screetching noise; however, it may cause leaking, so I would use that option as a last resort.