When starting our volvo penta 3.0 this year one of the freeze plugs on the port side of the engine block came out. Is it possible for these plugs to come out without the engine freezing? We completely drained the block and water pump last fall so I am puzzled and concerned as to why this came out. We cranked the engine quite a while before we realized we had disconnected the ignition wire. It doesn't seem likekly but could this cause it?