Black oily exhaust
Hi, my boat has an old Yanmar YSE8 8Hp which starts up first go every time, and when in neutral, runs really well. Until just recently all was fine. Then the last couple of times we went out, the engine does not go very well in gear (barely pulling 1.5knots under full throttle!!), and there is a black oily slick coming out of the exhaust. Since the oil level does not change, I'm assuming this is unburnt diesel. Obviously I'd like to get this fixed ASAP, but would like to know if anyone has any ideas of what might be causing this? Many thanks!