Cold starting
You did not give any indication of the age of your engine nor the hours on it. There are some old age problems that could affect starting but I will assume otherwise. You state that when you crank the engine it turns a few times and then nothing. That starter motor should keep on cranking until the batteries go dead. A word of caution, be sure that your sea water sea cock is shut off until the engine is started. If you have cranked very much without starting you could be filling your muffler and thence the enine with sea water. If it is water in the engine that is keeping the starter from turning it, drain the muffler and then try cranking with the compression releases actuated. If it is not the fault of water, the required current is not getting to the starter or the starter is not using it properly. The colder it gets the mor critical cranking speed becomes and the more difficult it becomes to have electrical current pass areas of resistance. Everything must be right to properly start the engine, especially when the engine is cold. You must have high cranking speed. You must have good fuel, not doctored up old fuel. You must have good compression. The high compression of a Yanmar diesel precludes the need for glow plugs. I could rattle on forever. How about give us some more information. Are we working on a cranking problem or does the engine not start when it cranks well? Also, describe the line that runs from your fuel lift pump to the injector pump. Is it rubber or steel? Of what era is the engine?. You have a good engine that can be made to start promptly.
