My Yanmar 3GM engine only has 142 hours on it. The engine started knocking and blowing smoke yesterday so I got a tow. We checked a number of things and when I pulled the oil dip stick oil gushed out and is very thin. The next day we pumped out over seven qts.; should have been less than three! It is thin and most certainly has diesel fuel in it. My mechanic thinks a faulty injector pump or a bad injector though he said these are rare occurrences and he seems unsure. I am on a freshwater lake without much of choice in mechanics. Any thoughts as the source of my problem?