Thanks guys, it sounds like we can just ignore that sensor then. I will have him run it and check for codes and sensor temps after it warms up. It had a problem where it would cutout trying to get on plane, but we changed the crank sensor and that problem appears to be fixed. It wouldn't start at the end of a day, but it was hot out, so maybe it was vapor locked. I will update when I find out more info and we do more trouble shooting..

Most likely you don't have the lake/sea water temp sensor/transducer installed on the bottom of the boat. so this would be the default reading from the boat's transducer being unplugged.

The lake/sea water temp "sensor" would be located inside thru hull transducer going thru the bottom of the boat to read the actual water temp of the body of water the boat is sitting in.

The PCM is designed to ignore this reading and a few others as far as engine guardian mode goes.