Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 183Get this manual
4Use 12 inch (12.7mm) drive on belt tensioner arm to relieve belt tensionRemove belt 1998 Model
aBelt Tensioner
If engine has been recently run, air pressure outlet hose fittings may be extremely hotAllow components to cool off before beginning disassembly