OPTI alarm question

I have a 2006 115 Optimax. It a occasionally beeping with no pattern or timing. Sometimes it will run miles without an alarm and sometimes it would beep once on holeshot an then again once or twice widely spaced while running. It does not hesitate when this occurs and it starts without flaw. I have changed everything except the sparkplugs so far. The only speculation is that the oil reservoir on the engine has a float that could be sticking.