Wow, this forum is the business, thanks for all the suggestions.
I forgot to mention that we re-conditioned the head
out all the waterways, new valve stem seals
, reground the valve seats and tested
I also cleaned all the rest of the engine waterways with Rydlime (very good) and fitted a new thermostat, washed air filter foam, spotless clean prop etc.
I cleaned out the pre-combustion chambers and fitted new insulators and copper washers so I'm sure I have just one installed but thanks for the suggestion. I also refurbished the sail drive unit so no issues there.
There's several other really good suggestions that I'm now keen to try so will be doing the following next:
1. Check that the thermostat is working at correct temp (80 deg C ? )
2. Getting the injectors Pop tested
3. Checking the injection timing again but this should have been done when the pump
was tested and reset but no harm in asking what the timing was set to (15 +/- 1 BTDC is correct?)
4. Double check air intake
5. Diesel cetane booster - why not !
I'll give this a go and report back with progress.
Thanks again to everyone who chipped in !!