What happened to the lower unit on my outboard or outdrive?  Should have I somehow winterized my boat's lower unit?  BEST PRACTICE------LOWER THE OUTDRIVE OR OUTBOARD DURING FREEZING WEATHER!  Yes, while it is true that for decades now most boat engine manufacturers have put a small hole at the base of the lowerunit that is supposed to drain the water out of the lower unit, IT CAN STILL HOLD WATER....FREEZE and then BLOW-UP. 

How then does this happen?  Most often you will not even know or recognize that you might have hit a submerged log and the result may not even be a bent prop....but there is a very likely prossibility that the little hole, that is supposed to drain the water from the lower unit when you raise your outdrive or tilt your outboard, is clogged up.  So keep your outdrive or outboard in the down position during freezing weather..... and for good measure...make sure the little hole is unplugged.  I have seen tournament fishermen, while on the road and reluctant to lower the outboard while at a hotel, for fear of forgetting to raise it up early the next morning when heading to the ramp; have their lower unit blow-up because they in-fact hit something during the first day of the tournament and the hole became stopped up and there was a hard freeze that night.  So check the hole regularly, as your wife will really give you a good reason to need a new lower unit if you allow the one on your boat to need replacing.