During a recent 3 week cruise of 533 NMs from New Bern to Charleston and back via the ICW, I put 97 hours on a 6-year old 27 hp Yanmar 3GM30F that has operated 650 hours. It seemed like I had to add a lot of oil during the trip. The total oil capacity is about 2 3/4 quarts and the effective capacity is about 1 3/4 quarts. I probably added a dipstick's worth of 40 weight oil, maybe a quart and a half or quart and three quarters. The rated 1 hour output of the engine is 3600 rpms, with a 3400 rpm continuous output. Most of the time I ran the engine at about 2800, or about 80 percent of its capacity. The engine temperature stayed about where it has always been. Although I did notice white exhaust smoke from time to time and a diesel smell. The oil change interval is 150 hours and I've always changed it at the end of a season (somewhere between 50 and 150 hours). That interval suggests the engine may have used an excessive amount of oil during the 97-hour cruise. Or it may mean that I used almost a season's worth of the engine in 3 weeks and oil usage was about right. Does anyone have some thoughts on this? Thanks.