Last year I purchased a boat with a Beta 38 with 75 hours on it. Because the boat sat unused for probably a couple years before it was sold to me, I did all the maintenance things like changing the oil, filters, etc. and then motored about 125 hours, the engine worked great! This fall I wanted to replace the coolant (and add a coolant temperature sender). Today I read the manual on that topic and found the location of the drain plug on the port side of the engine. It is difficult to get to because of the heat exchanger, oil filter, etc. (and it is a small engine compartment). I cannot see the plug but I can feel it. So I screwed it out expecting a flow of coolant but to my surprise nothing came out of the drain hole (I did remove the coolant cap at the top of the engine so there should not be an issue with pressure). I removed the plug completely and have attached a photo. I'm wondering what the problem might be that causes no coolant to come out. I thought of trying to insert a wire into the hole to see if it might be obstructed by corrosion or... something. But then thought it might be a better idea to post the problem here and see if anyone has experience with this situation. I'd like to get some advice before I do something that I might regret later!
Any suggestions on what the problem might be or how I should proceed?