Yanmar YSB8 issues
Iíve had a few issues with the 1976/77 Yanmar YSB8 on the boat I bought this June. The surveyor insisted that I replace the plastic tank that had been used to replace the original metal under the cockpit floor (evidently the plastic tank was too close to the engine to meet code). Anyway, I was going through the old fuel in the plastic tank while waiting for over a month for my new tank to get finished. With about 3 gallons left in the tank, I went out on a particularly rough day. Upon my return, as I put in her reverse (at idle speed) to slow down at my slip, there was an large puff of black smoke. The exhaust was already running black so I figured I was into some bad, old diesel and it would be best to wait for the new tank and fuel filter. I did.
The following were replaced: the tank, the fuel filter (with a Racor 120AS), and the fuel lines to and from the filter. The mechanic drained the old tank in the process and the Ďfuelí smelled more like turpentine than diesel. He said it must have been several years old to smell like that. I also suspect that the previous owner didnít top the tank up in the winter. Anyway, with the new tank, new fuel (after reading a fair amount I went with a 20% biodiesel/80% diesel blend), new filter and new lines, everything seemed to be great. The exhaust went from black to mostly clear. If I put the throttle forward it would put out a bit of white exhaust and then return to clear fairly quickly. So, everything seemed good.
To get from the slip to sailing typically involves only about 5-10 minutes of motoring. The other day, maybe the 3rd time out since the new tank, etc., the wind died and we motored back for about an hour. In the process, the oil indicator started to flicker. Besides that, everything seemed to be running well. The next day I checked the engine when it was cool and found that the oil level was below the lowest point on the dipstick. (The oil had been changed in June so this mechanic didnít check it, however, we did notice an oil leak.) It took 1L of oil (out of 1.7L total capacity) to get to the mid way point on the dipstick. I took her out for a great dayís sailing and for the 10 minutes out of the marina the engine ran great (little exhaust, etc.). She also seemed to run great the whole way back until I put her (again at idle speed) first in neutral to glide down the dock into my slip and then into reverse to stop. For this minute or so she started to put out a fair amount of white exhaust and there was a slight burning smell reminiscent of barbecued steak (someone in the marina might very well have been cooking but I donít remember smelling anything after the engine was shut off). When I opened the engine compartment afterwards everything looked and smelled fine.
Could the large amounts of exhaust (constant large amount of black exhaust with the old tank/fuel and now the recent 1 minute episode) somehow involve an internal oil leak and/or the engine burning oil? I recognize that the external oil leak somehow needs to be fixed if itís draining 1L of oil in 4 months, but Iíd sure appreciate any insight/ideas into what to do about everything else.