The original prop should have been a 14 1/4 dia. x 21 inch pitch. The Volvo/OMC outdrive propshafts and props have a different number of splines than Merc and other brands. I believe the Merc has 15 splines, and the Volvo has 19 splines.
Go to the
www.Fourwinns.com site and click on "Owners". Select the year. You can find a lot of general info for your boat in "Fast Facts", Owner's manuals, Parts catalog, sales brochure info, merchandise, and more.
The Fast Facts identified the 14 1/4 x 21 prop. This is a common size prop that has been used in many different boat/engine combinations. Volvo/OMC changed the gear ratio in the outdrive to work with different engine power choices.