mjlash22

Hello,

New to the forum! I have a 2017 Searay SPX 210 with the Mercruiser 4.5 (200HP). It has been a horrible boating season thus far. Early June, service light came on. Took out of the water later that month and dealer said 1 of the trim senders assemblies went bad (3 wire/1 puck version). Got it back from the dealer, launched it, and not even 5 minutes later, light was back on.

This time, I decided to purchase the Mercury Vessel View Mobile, instead of the $100 per time computer scan from the dealer. Code is reading as follows:

851-11: O2 sensor Port S2

Does anyone know if this is the pre or post CAT sensor or should I just do trial and error and replace one to see if it corrects? Is it possible it's not even one of these sensors at all?

BUP

iTrader: (9)

851 is post cat and the 11 means lean condition. No offense but not that much info to be had for production catalyst marine engines on the forums. I work on these and been thru many training programs from the OEMs.

mjlash22

Thank you for the info! I ordered the part and will swap it out when it comes. Hopefully this is it and not something deeper in-bedded.

BUP

iTrader: (9)

the easiest test to do is swap post O2 sensors and see if the code shows - 871 - 11 - then that would tell its the O2.

871 is post cat starboard O2

BUP

iTrader: (9)

the easiest test to do is swap post O2 sensors and see if the code shows - 871 - 11 - then that would tell its the O2 issue itself.

871 is post cat starboard O2

mjlash22

So silly question, but are the post/pre O2 sensors different or are they the same part number?

PA.WOODCHUCK

doesn't that fall under the emissions warranty?

mjlash22

BUP

iTrader: (9)

engine serial number tells it all. Early cat versions were Narrow Band O2 s and then they went to wide band and narrow band O 2 s

BUP

iTrader: (9)

warranty depends on years of ownership and hours for emission controlled engines - warranty is 480 hours its over with EC engines