engine alarm and white smoke!

[jwclbi]

Hello, heres an interesting one. Im running back home and all of a sudden the alarm goes off and my 225 efi merc is blowing white smoke out of the exhaust! Im thinking blown gasket. I stop the boat let it idle for a couple seconds shut it off and check a few things. water was pumping, oil level was fine. Was getting dark soon so i thought well let me see what happens if i fire it up again. start it up, runs fine, no white smoke, no alarm. Ran perfect the rest of the way back, about 20 minutes. maybe a thermostat got stuck? any thoughts would be cool. thanks