Can't think of any. I've owned the Yanmar for 6+ years and it has been great. In the design of my boat the maintenance access is great. The impeller for instance is right on the front of the engine, although other Yanmars do have the impeller in a difficult location for access. Doesn't use a drop of oil between changes and the oil remains clean. They do emphasize that maintenance is important like changing the antifreeze, which I never did on the westerbeke/Perkins. It does use more fuel than the other engines, around 1 gal/hr but the boat is much bigger and I cruise at around 7.5 - 8 kts where my previous boat made around 6 kts.