Cooling system question

[SATige]

What does this thingy do? Mine is leaking at the drain plug, the tighter I make the plug the more it leaks, there's obviously a crack at the threads. It's an expensive part, just wondering how important it is that I replace it due to the leak.

Thanks in advance!

[JCP]

That water housing has the optional air pressure to winterize feature. #10 and #11 are the air pressure line fittings. If you don't want to buy a new one, try to Marinetex the drain plug into the housing and around the where the crack is. You will need to pull the bottom hose when you winterize instead of removing the plug.

[boatwakes]

That thing is another of Mercruiser's plan to sell parts, idiots over there. Some have air fittings and some don't. You can replace the whole unit with a bronze tee and elbow sized for 1.25" hose facing engine aft and 90* and 1" hose going vertical. It doesn't matter if it's got the air fittings or not to replace it. Use 4200 marine silicone, Marine tex dries hard and won't allow for the crack to be filled. When you remove the blue plug, replace it with new.

[SATige]

Boatwakes, thanks for the info. Mine doesn't have the air fittings and the cap (part 5) seems to do nothing. I like the idea of sealing the plug in place, I'll give that a try.