I recently had some experience in the area of mechanics on my 1975 vintage sailboat. My old one cylinder Yanmar was knocking loudly. Even though this is the second time I have owned this particular engine in a sailboat, I had never experienced this noise. I once had to call a mechanic when the high-pressure delivery pump failed on my previous sailboat, but the engines are pretty trouble free if you maintain them regularly. Apparently, I was fortunate to find a mechanic nearby that was willing to leave the multi-million-dollar yachts at Ocean Reef to work on my humble dreamboat. My latest experience was totally different. Since I had a good experience with the mechanic in the past, my first inclination was to call the mechanic. I spoke with him three times over a period of about a month. Although he gave no direct indication that he didn’t want to look at my engine, he kept putting me off and just wouldn’t call me to make arrangements. Another attempt with another mechanic/dealer resulted in a diagnosis that my engine should be replaced with a new or more up-to-date rebuilt model, because the parts were getting hard to find and expensive. Before I knew it, I was calling and pricing engines. I guess it is human nature to look down the easy path first for a solution. The sticker shock of new engine prices plus labor and my lack of cash finally brought me to my senses. By this time I had already said a prayer or two, as well. No body had looked at the engine besides me, and I had been willing to consider replacing it. Somebody slap me, please! Here’s where I would normally have exhibited another human characteristic, self-reliance, but I felt weak in this area of knowledge. On my many visits to the bookstore to browse the titles on boating, I had noticed several books on marine diesel mechanics. I bought one. It turned out to be a very good guide for maintenance, but didn’t appear to have an identifiable diagnosis or solution to the problem. Back I went to the bookstore to buy another book. This time I found Nigel Calder’s book. It did not just describe the problem and then give a solution. It told me how to troubleshoot the problem in order to reduce the possibilities. With my son’s assistance, we ran the test for identifying the source of the knock. We were ready to celebrate at the result, because it eliminated all the worst possibilities. It was not a mechanical knock, but it sure had sounded like metal clanking. In his book, Nigel had pointed out that mechanical and fuel related knocks could be indistinguishable. The test had been so simple. You run the engine at high Rpm’s then suddenly put the throttle in the off position to cut off fuel to the engine. The engine then coasts to a stop. While it is coasting a mechanical noise will continue, but a fuel related one ceases instantly. Since the noise had ceased, we checked the torque the bolts on the head and checked the valve clearance and changed both primary and secondary fuel filters and vented the fuel system. The knock was totally gone! Oh yea, I also found out that parts are available and not very expensive. It would have cost about $300.00 to $400.00 worth of parts to rebuild the whole engine. The engine had appeared to me to be a black box of mystery, but now I was in love with it! I will not be so fast with the wallet next time.
