Having trouble on initial starts lately. Tried it on a hose in the driveway. Very difficult to get it to fire. Once going she seems ok. Did notice that I get a little black sludge out the exhaust once I shut her down. Drips down the skeg. This morning I fired it up, after difficulty. Once she fired, she spit a lot of black sludge out the prop. Any thoughts appreciated. 1988 200XP