I noticed on my last fishing trip that my oil pressure gauge no longer goes back to zero when I shut off the motor as it once did. It holds at about 15 and seems to work fine and read normal when at speed going from location to location on the lake. Any idea what is going on here and can I adjust it back to zero?

Most oil pressure gauges are electric with a 'pressure sender' driving it from the motor. If your gauge goes to zero when the ignition is off, then the problem is probably in the sender. If is doesn't, then replace the gauge.

Thanks