Something you do not mention but have probably checked.
On some of that family of engines it required the coolant return pipe at the turbo bleeding when refilling the system.
Although from what you describe the coolant is being forced up out of the header tank.
I am not sure if it applies to...
I seem to remember that Fairline used to note the prop sizes on the printed price list which was separate from the brochure.
No doubt someone may still have tha info in their Collection.
Worth a question on the Fairline Boats old and new facebook website.
Looking at Aft Cab Mirage on net appears to show stanctions and wires fwd so should be able to replicate aft provided access available and stanction footprint allows.
I was sent this today.
Absolutely spotless note ths rocker covers.
The boat is American built Westport 40m.
The engines are MTU 2750HP
Spotted 3 out of place items.
They have 2 tenders one being 39 ft centre console 4 x400hp outboard which they tow when changing locations (Bahamas)
Brightens up...