I just changed my impeller, when i first launch the boat after a few min at idle the alarm will sound, temp is fine so I put it in gear to go fwd slow and alarm goes off. does antone have a clue

It could be one of the many sensors on the motor. Get it scanned and it should give you the culprit.

Check drive lube reservoir. Low level will trigger alarm.

my drive res was making mine go off and it was full. i unpluged it and boom it went off. so i replaced it.