I have recently recieved a 40+ year old sunfish from a neighbor who has used it twice. Now this has been sitting in his yard for a good 38+ years. (Excuse my lack of usage with nautical terms.) Now I've emptied all the water I could but now this white semi solid concoction is under the drain. I don't know the first thing about sailboating or sailboat repairs etc. etc. So I'm not positive if I can take off the top or I'm missing another orifice of the boat lol. Any help is appreciated. Thank you.