Hmmmm, 4000hrs is getting up there for a wee 3. And especially if it was worked hard while overproped. It is hard on main bearings. It can also leed to holes in the pistons, but that is either a go/nogo failure.
However, as Chris has also stated, if it is not showing any major signs, it still could have a lot of life left in her. At least with Deisels, it is rare that you get a sudden failure. Not impossible, just rare.
As for the motor
, you will find no hidden surprises. Nor a zillion seals etc. They are well engineered and not overly complicated. I suggest a strip down and send the block to an engine reconditioner or engine machine shop or what ever you call them your way. I imagine the crank will need ground and then oversize bearing shells to suit. You won't want the Journals bored. IF cylinders are bored, then it will mean new pistons.
Mate, I know of a 3 cylinder Yanmar here for sale
that has done next to nothing in hrs. It is a few years old, but I doubt if it has even reached 300hrs. I know the motor
, the boat and the owner well and can vouch for them all. The owner doesn't want a lot for it. I wonder if it would be cheap
to get over to you.
What is it going to cost to recon yours???
They are about NZ$13K new here. You would probably get this one for NZ$4.5-5K. That's about US$3500 at most to you. Let me know if you want to pursue it and I could investigate it further for you. Just a thought.