Mercury Outboard V6 Gearbox Also Fits Mariner. | eBay
(I have a 1989 Black Max 135 & according to my workshop manual which covers it the 135 & 150 have the same gearing of 2:1 as does the early 175 but above serial number 6618751 the 175 is 1.87:1. I don't know if yours being 2002 will be different - presumably an Optimax? - but best to check.)
if you click on the link in Turbodiesel's post (black dog) it shows East Looe Cornwall.
They do rattle a fair bit if you engage gear slowly.