Yamaha F70 Alarm

I have a 2011 Yamaha F70 (four stroke) that will have a steady alarm go off only when I am Idling or slow trolling and only after a long time. If I shut off and turn back on it will not come on for a while, it will also go away when I speed up. Appears to have a good pee stream, but I am thinking it might be the impeller/pump. I know the oil levels are fine and the water fuel separator is fine. Lower unit has been serviced with no changes. Any other Ideas would be appreciated.

Could still be the impeller. When was it last changed?

That's what a friend said. Have it in the shop right now. Thanks