1999 mercury 250 efi blue water beep and rpm limited

[mountttech]

I just got a boat with twin 1999 250 efi blue water engines, when we test drove the boat its was fine no problems. The first time I got it home and took it out the starboard engine warning light came on and alarm. It goes like this " It blinks from the oil light to the temp light and beeps as it alternates." sometimes i can speed up and it stops sometimes i can slow down and it stops, sometimes it does not stop and i have to turn the engine off for awhile. The second trip out the starboard engine was the same problem, then out of the blue the port engine went like this " oil light came on then a single beep then light stayed on for awhile" after restarting the engine it went off and ran fine the rest of the day. So i checked the oil tank on the side of the engines and they were full however the starboard tank was full to the top, when i opened the cap the oil went down to the input level line like the port engine. Took the boat out today and the same thing happened again with both engines only now at wide open throttle the rpms are limited to 1800 when in gear. In neutral they will rev as high as i want them to. The boat runs fine on ear muffs as well. Any help would be great, Thanks.