500efi -- Where are the block drains?
 

This is probably an ignorant question, but I'm getting ready to winterize and wanted to know where the block drains were on a 500efi before I got in and started fumbling around like a complete idiot.

Bottom sides of the block, not far from where the car motor mounts are located. They are lower, one per side.
If you have water pressure gauges, they connect them to the block drain.

Fixx
 

and the other side probably has a knock sensor in it..

On mine the knock sensor is in a different hole. And they have a bronze fitting with a blue plastic finger plug in them. Also check the coolant hose below the circ pump and cool fuel for plastic plugs there also if you are trying to drain the whole system.

As Wildman said, since you have a Fountain, the water pressure is probably hooked up to one of the drains on each engine. It will probably be the outsides of each engine where the hose is. Just disconnect the hoses and let it drain. You will then have to pull the plugs on the insides. It will be in about the center of the block just above the oil pan rail.
Eddie

One of the block drains is just in front of, and slightly above the front end of the starter on each engine, where the wires from the battery attach ... that is the easiest way I can describe it. Be sure to turn your battery switches off before you put a wrench (or a socket on an extension) on that block drain. Don't ask how I know about turning the battery switch off, first ;) .... Sparks will fly!! Usually, there is nothing attached to that drain, it should be just the brass plug. The other drain is on the other side of the engine buried below the head and above the fuel cooler (I think that is that cooler). Anyways, that is the block drain that Fountain usually uses for the water pressure gauge. They usually use a 45 degree flare fitting, if I remember correctly. On the starboard engine, it should be on the port side (ie, in between the two engines), and on the port engine, it should also be on the port side. Good luck getting to the block drains that are between the engines. Easiest way is to remove the headers. I don't remember exactly anymore, but I think the alternator is mounted down low too, so you may be able to remove the starboard engine's alternator to get your hands back in there (where the drains are hiding), too. I do remember it was not easy to get to those drains. The last couple of winterizations, I paid someone else to do it. :D