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While someone cranks the engine, take a meter set on 1 volt and go from the center of the post on the battery to the cable connection right next to it for positive and negative battery posts. Also go from negative side of battery to engine to see if there is a problem with the ground. Anything more that a few tenths of a volt should be cleaned. Also check any starter relay connections. Make sure you have more then ten volts across the battery while cranking. A diesel needs to be spun fast to start. The way it works is compressing air makes it hot, so hot that injecting diesel into the cylinder will cause it to burn, but you have to spin much faster than a gasoline engine. You also need glow plugs that work to get the air going into the engine cylinders hot, especially in cold weather. Put simple hand held compass against the wire going to each of the glow plugs and see if it defects when the glow plugs are turned on. Electricity going through a wire makes a magnetic field the compass can detect. Batteries on boats are prone to sulfation caused by not having them fully charged. If they sit discharged, even partially discharged for a few weeks, sulfation can happen. Google sulfation with the word battery. Sulfation will prevent a battery's charging and if a battery is dead and has sat for a while, you just have to get a new one. Swap a good car battery in there temporarily and see if it starts. Check fuel filters for water. In your situation water is probably not the cause even though it is about 80% of the time for running problems so just check it anyway. A final thought is the starter may have a short. Would have to check a Perkins 18 hp diesel manual to see what the normal current draw would be. There are hand held DC meters that you hold against a starter cable that read the current in a starter cable by detecting the magnetic field around it. Shorts will be at least five times normal.
Last edited by LakeSuperiorGeezer; 11-14-2010 at 10:47 AM.