I have a 2000 225hp and just had the O2 Senser replaced and didn't get the best explanation about what it's purpose actually is. Any help out there from a night owls?
Sure -- It's just like it your car/truck. The sensor "reads" the exhaust gases and tells the computer if the air/fuel ratio is correct for the situation. The computer combines and process the information along with other factors like intake air temp, vacum level, and constantly adjusts the air/fuel mixture for "optimum performance" as set by the maufacture.