The service required display usually comes up when a sensor is out of range, not when the oil needs to be changed. It is like the check engine light in your car. If the cause of the ecm code is corrected, the display will reset after 3 heat/cooldown cycles (engine runs above 150 deg then below 100 deg, 3 times). Otherwise the only way to find out what the code is and to clear it is to hookup a computer with marine service software like rinda diacom. If you have a good indmar dealer in the area (supra,moomba,malibu,mastercraft) it is likely best to take it there to get it taken care of. Sometimes a bad exhaust temp sensor or even a bad speed/temp/depth triducer will cause this (or a number of other things). You won't know until you get it checked out.