in most cases, in order for coolant to rise and circulate, there has to be coolant, and in a quantity to reach the water pump. If it reaches the water pump, and the water pump works, you should see circulation. Although I am unaware of the circulation system in your boat (IE closed system: radiator, open system: lake/sea water) I am pretty sure you may have A) low coolant level, B) bad water pump, or C) a blockage somewhere. Diesels make a lot of heat, so I wouldn't run it long with out the cool juice running through it. Start with the easiest, by checking the coolant level, then check the V-belt tension, to make sure the pump is spinning, then check the pump itself . If you have adequate coolant, check to see if the seeping becomes leaking. I would think that you should see coolant moving when ever the engine is running, unless you have a thermostat, then you would as soon as the thermostat opens. Let me know what you find. I have a little outboard, and don't know much about inboard/outboard setups, but engine cooling is, well, uh, engine cooling. There isn't much to it.
Greg
