It would also mean ring failure as well.... but could also be me worrying about nothing. The air filter foam did fail completely (at present i've removed the filters entirely), so it could be just diesel saturated powdered foam... and frankly, the injectors were just a little soiled, not dripping!
I did notice that the fresh water system needed filling a fair bit, so the other disaster scenario going through my head is a cracked block.... it could be paranoia, or perhaps a little less cataclysmic, and just a failed head gasket.
I have also spent a couple of hours watching Youtube clips and googling, and its apparent that the pump isn't working as expected. There is plenty of Youtube material of injection pumps, showing a good squirt of fuel from each port on top as the engine turns over, and that's not happening... so its still either airlocked, the fuel pump has failed, or the injector pump is siezed... i do however, now know how to have a go at freeing the rack in the pump if necessary. I'm slowly working through the problems.
Plan of action now.... after the yard have taken a peek, oil check, a good inspection on the fresh water side, and then I will deal with the raw water pump as a matter of priority, before spending loads on injector pumps etc.
I have that dillema that faces a lot of boaters over when to stop spending money on the engine. If the core is sound, then a new set of ancilliaries is no bad thing, but I do need to get to the bottom of the problem quickly, as if it needs a complete rebuild, new rings, bearings etc, then I have to take good look at the cost.... and if the block is scrap, then is good night and good bye to the Lehman!
Sticking with positive thoughts, if I do get past these hurdles and still end up with the Lehman, then i'll know the engine a lot better than before!
Finally, my friend Nev has offered his help, which I may well take him up on, particularly as if I end up removing the injector pump, setting the timing is new territory for me, and some experience would help a lot... thanks Nev!