OK, experts. Armed with all your good infomation, I went to see the boat today and have a test out. The "story" of the engine rings true to me. It appears to have been well looked after by an competant owner who knows what he's doing, or at least has learnt.
I saw the engine start, from cold, on almost the first compression stoke straight to a slow idle. That's good. We did a few miles along the GU and a couple of locks, so I got to try the handling and see how the engine performed under load (very well, just a hint of black smoke from the exhaust, no misfire, a wonderful exhaust note). Oil pressure stayed steady at 32 PSI 'till hot idle, when it dropped to about 20.
Inevitably the visit has raised some more questions so I hope I can get some more advice here.
The owner said that when he rebuilt the heads, he had repaired the compression change-over valves, but after a year or so, they, had started to leak again, so they had been plugged permanently on the high compression setting. Is that legit, or is the engine beating itself to pieces running high compression all the time?
The idle speed hunted a bit, much more so when cold, but a bit even when hot. Is that anything to worry about?
One of the injection pumps was visibly leaking diesel. Performance wasn't affected, as far as I could see, but should I worry about oil dilution? The engine has a dry sump and huge oil tank, so there was a lot of lube oil to dilute.
The Lister-Blackstone manual box was a bit noisy astern. Gear whine, not unhappy bearing noises. Is that reasonable? Neutral was difficult to find: small movements of the gear lever in either direction started the prop moving slowly. Is that sinister, or to be expected?
Oh, and thanks, Mike, for the offer of a copy of the FR book, but the boat comes with a full set, so if I buy, I'll have all the information.
Cheers,
Simon.