Boat owners...do you guys always winterize your boats each year?  What are the chances of ruining your outboard if you did not?  

My father-in-law has an old boat, which he never does, but each year it keeps on ticking.  

What's your opinion?

A few things that may happen:

When sitting for long periods, the gasoline breaks down and may clog up the fuel delivery system in the engine. With some of the high performance engines the octane change may cause a blown engine.

That is usually the only time that the lower unit is checked for damaged shaft seals and any water that may be in the lower unit will freeze and crack the housing-if you are a freezing part of the country.

The combustion cylinders may get some rust in them from condensation and may fuse the rings to the cylinder walls and damage them-Not a good thing.