My apologies in advance if this post is/seems stupid .... I just don't know where to start.
Setup:
1984 Cranchi Hobby 190 (19 feet)
Volvo Penta AQ175A (should be 170 HP?)
Volvo Penta outdrive (I think 280 -- how can I identify that?)
If the outdrive is indeed a 280, it should have a ratio of...