I purchased a new to me 21'Regal last month and did some repairs(bellows,manifold gaskets, gimbal bearing, filters and fluids.)I had it out a couple of times and it runs great. I may have to winterize it soon due to some health issues. I did not have time to run all the fuel out of the tank which I wanted to do because it had a 1/2 tank of fuel that was sitting for almost two years(51 gal fuel tank). I did fill it with fresh fuel and added stabilizer. Do I need to add anything else to the fuel now or in the spring? Also, the engine is fresh water cooled(3.7 Merc)New antifreeze was put in. Should I put anti-freeze in the heat exchanger(seawater side) or just drain and leave empty?Thanks for any advice.