I have a volva penta 4.3 on a Sanpan pontoon. While running the boat today the check oil light came on. Oil pressure was good prior to light coming on. Turned boat off and light turned off and did not come back on again. Ran another 15 minutes with no other problems and good pressure. Checked dip stick and oil level was good. I did not change the oil this year but oil only has around 20 hours on it. Any ideas what issue could be?