As someone who is still waiting for the right used boat to come up for sale, I'm trying to get all my knowledge in order. So this leads to: What's the deal with winterizing your boat? Is it a MUST or just recommended? I know it entails stabalizing gas, fogging the engine.... blah blah and thats about all.

It includes more than stabilizing the fuel and fogging the engine.  Fuel filters should be changed, and lower unit lube should be changed as well.  If the lube in the lower unit shows any whitish coloration it shows water intrusion into the gear case.  You may consider checking the water pump (I have that done along with the rest of the servicing).

 

All the pivot points on the engine should be greased or lubed.  It's a good time to "nut and bolt" all the fastenings for the mounting bracket, steering, etc.  It's the "ounce of prevention being worth a pound of cure" adage.  Fuel lines should be checked.  Electrolyte levels in all batteries should be checked and distilled water added as needed.

 

It's also a good time to go over the boat from stem to stern and make sure everything is in good working order for the next season.   Batteries should be kept up to snuff by periodically charging them when a boat is laid up for prolonged periods.

 

That's a few items to tend to.  I'm sure I've left out a few, or maybe several.

It's only a must if you will store the boat. What Rhino mentioned should be done once a year whether you winterize or not. I also remove the batteries from the boat and grease the hubs on the trailer to make sure there's no water in the bearings. If the boat is stored outside, trim the motor down and cover the lower unit with plastic to prevent water from entering. As far as gas treatment, either use/drain the fuel and store it empty, or fill up the tank and stabilize. A partially full tank will allow condensation to form. Water mixed with fuel is not good. There's a ton of videos on youtube showing how to winterize the motor.