The fuel system is very possibly "frozen-up" because of stale "varnished" fuel. This can cause the injectors, fuel rack and the injection pump's plungers to stick and not deliver fuel. The entire fuel system should be thoroughly checked and repaired if needed prior to starting the engine. The sea water pump impeller, if not removed from the pump, can take the shape of the interior of the pump. The pump impeller can also be brittle - check it and replace if needed. If the engine wasn't fogged prior to decommissioning, or if it's never been run, there could be some rust in the cylinders. This can be addressed but we strongly recommend it's accomplished by qualified personnel only! Remove the glow plugs or injectors and squirt a good quality lubricating oil or penetrating oil such as mystery oil into each cylinder. This will loosen up frozen rings and sticky valves. After letting the oil penetrate the engine's internal components for a good period of time, turn the engine over by hand with the glow plugs or injectors still removed. After you turn over the engine by hand (glow plugs or injectors still removed), use the engine's starting motor to crank the engine. The oil pressure will build up and be forced through the oil passage ways. This will lubricate all of the components that are normally well lubricated by the system in normal operation. IMPORTANT NOTE - cranking the engine with oil in the cylinders can cause damage because oil will not compress. The oil in the cylinders must be evacuated before reinstalling the glow plugs/injectors and trying to start the engine. Replace the lube and fuel oil filters. TIP - if the engine is layed-up for an extended period of time, turn over the engine by hand occasionally.