Just bought a boat with a 1998 Johnson 150HP Oceanrunner engine. Runs great,<br />starts every time, idles well, sounds normal, no smoke, etc. After running at<br />3500 rpm for more than 10 mintues, the check engine alarm sounds. As soon as I slow,<br />alarm ceases. No symptoms of anything wrong with the engine. Are these sensors<br />just too sensitive? What does the check engine alarm actually sense? Thanks-