Question about Seloc Yanmar Inboard Diesel Engine Repair Manual SEC-7400

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Yanmar 1 gm

The engine has been in a wet environment (there has bee water in the bottom of the boat, for a period of two months), and it has been down to minus 15 degrees C. Now, as I try to start the engine, it will not turn. My theory is that the flywheel will not turn, due to rust. What do you think of my theory, and what must I do, if I am correct?

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Im not sure what all you have checked, but I would first determine if the starter is engaging and spinning properly. Put a good socket on the end of the crank with spark plugs out and see if your theory is correct. If I misunderstood and you stated that the flywheel will not turn because you have already tried it then you have a stuck engine, more than likely the piston rings have a little rust. Try filling cylinders with Marvel Mystery oil. Some use diesel and transmission fluid. Fill completely and wait a full day then see if it will turn with plugs out. Repeat the process after a couple of days passed with cylinders full of oil. Do NOT apply a lot of force as this could break piston rings or worse. Make sure plugs are removed as this can put excessive loads on engine parts and rods can be bent. Chances are very good this will work. Be patient.

Posted on Jun 25, 2013

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