first does the crankshaft rotate?? Assuming it does, I would clean out the fuel tank
and all engine
fuel and oil
filters and change the engine oil
too. Bleed the fuel system.
Me I would crack open the high pressure lines at the two injectors. With the decompression levers depressed, and the seawater valve CLOSED, I would crank the engine for 10-15 seconds to get the engine oil distributed and maybe verify fuel leaks
from the cracked up injector feed lines.
Assuming all is good, tighten the feed lines at the injectors, OPEN the raw water
valve and see if it cranks up.