Hi there, On a MPI engine model, disconnecting each sensor isn't going to give you an indication if that's the sensor what's sounding the warning horn due to as you disconnect them you are creating a/more fault/s because the ECM see's the programmed sensor value fall out of the know range. Then when you or someone connects a marine scan tool and looks through the fault history, it will show them as a possible problem 'kind of making it a little confusing until the fault history is cleared and wait for the problem to reappear if it's going to. Disconnecting most sensors could sound the warning horn.
Carbureted engines are not affected by the above scenario.
When the problem sounding the warning horn is resolved, the horn will stop automatically and everything will work normally without the need of a scan tool to reset.
Without the aid of a scan tool, finding a fault code is difficult to find with mostly guessing until found. While there are a small number of "usual" problems found on the internet that could sound the warning horn, there's also a good number of other things sometimes not mentioned that could sound the horn as well.
