I think all the good points are covered. The key one is to find a mechanic who really knows their stuff. They need to do the compression test, or a leak down test, and probably to use a borescope to take a peek inside the cylinders. Good marine
diesels will run 5-10,000 hours between rebuilds, so you're in that range where how the engine was treated really means everything. Looking around, or asking your mechanic, for signs of neglect or good maintenance
, mean more than the number of hours. Does the fuel filter
show sediment? Is the fuel tank
really clean, or has sediment built up in that? Does the engine start quickly and run well?
You might want to have the fuel
injectors pulled, cleaned and calibrated, (all routine at any diesel truck engine shop) and have a mechanic show you what is involved in properly bleeding the fuel
system, as well as changing the water pump
impeller, filters, belts, thermostat--they may all be recently changed and perfectly good, but you'll need to know how to do that for routine maintenance anyway.
I'd disagree on the value of an oil analysis. For a whole $25 it *can* often tell you if there's catastrophic failure to come, and it will tell you if the current
owner has recently changed the oil with a proper grade. Won't always tell you everything, but for $25 it can tell you if there's a red flag, like high levels of bearing metal in the oil.
Incidentally, there's no such thing as a 'Westerbeke" engine. They put out contract
bids for everything, with varying results, and then assemble the parts
from all of the lowest bidders and slather red paint
over the finished job. That doesn't mean a Westerbeke
is a bad engine--just that it really always has a secret identity.