2008 yamaha 225 4 stroke alarm

[gsx99]

put the boat in the water this year (has been sitting for a season) every once in a while the alarm goes off I put it in nuteral and rev it and sometimes it goes away. other times I shut it down and start it back up and it stops.

this is bothering me because the channel has been extreaml low and i thought that it could be from crap but it has happen twice at ideal in the ocean

I had the water impeller changed about 40 hours ago. any ideas would be apreciated.