An outboard motor includes a cowling enclosing an engine, an ambient air intake defined by the cowling, and an intake passage introducing ambient air taken through the ambient air intake to the engine. The detection circuit includes a first block configured for generating validity signals that identify the memory locations containing valid data and a search circuit configured for determining a search pointer as a function of the validity signals. A bit line selecting circuit may be configured to selectively connect each of the plurality of bit lines to an output bit line. A control structure moves the gates to change the size of the openings. The biasing agent is disposed within the bore.