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My 2011 350 8.2 HO port engine...

Guest Contributor

My 2011 350 8.2 HO port engine shows fuel system issue. Vessel view shows oxygen sensors issue. So I replaced all 4 and spark plugs. When I changed oxygen and spark plugs they all where VERY clean

I had a local mercruiser dealer come

clear out codes and NO alarm codes for the first 2 hours  now I am back to alarm code and alarm beeping every 6 min

the boat runs awesome I am getting proper GPH burn, no rich fuel burning smell 

I am at a total loss can anyone provide some help?


Rising Contributor
Welcome to the forum.

This link has good info on identification then fixing O2 codes.

Guest Contributor
Thank you for the information it was very informative . Now with that said how do I check the voltage on the sensors ?
Do I have to have service tech come back out and hook computer to engine? If so
techs computer should be able to tell him that the before or after sensor is not working properly on either side or does tech have to hook into before and after senors directly to get info
I will check for vacuum leaks, restricted air or any wires not protected for grounding
Everything else would have to be done by computer
I will let you all know what happens in the weeks to come
Be safe out there
Happy boating

Rising Contributor
Use the correct Factory Service Manual (FSM) for that engine to determine the analysis / repair steps. Owning / reading / understanding the FSM is a required first step for performing service.

For my boat I purchased the Mercruiser Digital Diagnostic Terminal (DDT) to permit me to perform all the required analysis and repair.