Generally speaking the life span of a diesel is closely related to the maximum rpm the engine will turn. There are engines that turn 4000 rpm to generate 60 hp and there are engines that turn 2800 to do the same. The 2800 rpm engine is going to be built stronger, and probably weighs more, and should have a longer working lifespan all things being equal. In my experience the Kubotas have always been a tough, no nonsense engine but I'm not familiar with the latest models so can't comment on them. I would stay away from a new model that hasn't been around for at least several years. As far as parts availability and service worldwide I would think Yanmar and Volvo probably are number one and two, not sure which is #1. With overnight delivery almost worldwide I'm not sure how important this is though. I would actually look at each engine you are considering and think about where things are located and how accessible they will be in your boat. IMHO a turbo on that small of an engine is not only unnecessary but also a maintenance and reliability problem. A lot of manufacturers are using smaller blocks to save weight and cranking the hp up by use of turbos and intercoolers. If I were going to repower (I have a Volvo MD 31A, 62 hp, 4500 hrs) I would look at something non-turbo, low rpm, without an electric fuel solenoid (cable stop) or electric fuel pump. Let us know what you decide on, OK?
SV Laurie Anne
1988 Brewer 40 Pilothouse