2005 Crownline 225 w/496HO. Yesterday boat ran fine. Hauling you know what down the lake and buzzer went off. Immediately checked gauges and shut it down. Checked fluid levels...All ok. Started it back up and ran fine to about 3/4 throttle. Buzzer went off again. Lower speeds no problem - system at 90% and buzzer sounds off twice every minute. New water pump with 4 hours on it, all fluid levels ok and pressures are fine. Figured a bad sensor or maybe cooling system blockage. Today took boat out of water and checked everything out. No visual blockage and water seemed to drain from out drive ok. Pressurized drain system to drain water (like I do when I winterize). Everything seemed to work just fine. Put boat back in water and ran it a short distance. Buzzer went off with consistent buzz and temp started rising. I shut it off and there was a water running noise coming from engine. Opened it hatch and seen water pouring from the drain hole in the drain actuator assy. - engine is off. Thank goodness for bilge pumps. Towed back to shore by a friend. Thank goodness for those too. Any idea on what my problem might be?