the tools to need to inspect your 175 mercury gearcase can be bought at a reasonable price at this adress. I used to work with them, and you can buy also new parts , seal kit and what you need for your engine. If you have the serial number of your engine you have also the drawings parts list and prices. You can buy mercury tools or other similar tools but at a lower price. the web site is : Ishopmarine.com
Hope this help.