VP 2002 starting problems

I have a 1983 2002 engine which I have used for 6 years without a problem. This year it has taken excessive cranking to start despite using the cold start trick. When it finally starts there is a fair amount of blue/grey smoke for a few seconds with oil slick on the water, then this reduces to a faint blue smoke when warm.
I am aware that there could be numerous reasons for these symptoms but would like to eliminate them in order of: - a, ease b, cost.
I am a resonable engineer and would be prepared to rebuild the engine rather than re-engine. In the event of a compression problem and the associated costs, what is the life expectancy of this engine (Raw water cooled). Thanks in advance

Andy

Blue smoke indicates burning oil. I would check compression first, if it's low, it would explain hard starting. Rebuild time it seems.

Just for reference, and since I did not receive any real advice, I suspected a fuel issue rather than a compression problem. The original intention was to extract the injectors and conduct a compression test to eliminate worn rings.
On extracting the injectors (extraction tool built from scratch) it was obvious that the injectors were badly in need of a service. Both were serviced by a good diesel injection spe******t and duly installed. To eliminate any air related issues all the fuel supply pipes have been replaced after finding the olives nipped up so tight they had reduced the cross section by 50%. New primary and secondary filters. Valve clearances checked (cold).
The engine statred after only a few cranks to my utter suprise. She ran with with no smoke, sounds as sweet as a nut, no lumpy tickover, revs climb faster as well and she now revs out 500rpm higher than before.
The whole job cost less than £150 or a couple of hundred USD. Its worth trying before contemplating a new engine if you have poor starting or smoke related issues.

Cheers

Andy
Westerly Griffon GN392

Usually when their is a compression problem, pressure builds in the crankcase. This is what generates blowby. A little blowby is normal, but if it shoots out the dipstick, their is a problem.