Originally Posted by
EuropeanAM
PCM is monitoring temp and pressure- the "time" ignored applies only where the PCM perceives it may be a simple "curable heat soak". For a hypothetical example:
One warm start is at 168 degrees... engine starts, PCM sees temp begin to decrease within 10 seconds. At 15 seconds, water pressure begins to climb. PCM logic ignores and does not log any sort of overheat.
Another warm start is at 174 degrees... engine starts, PCM sees temp rise to 176 within 10 seconds and logs an overheat fault. 15 seconds later, water pressure begins to climb and temp begins falling. PCM sets the status of the fault as "inactive" (no longer occurring).
I believe you will find that the situation is more related to how high you have the engine, rather than how many holes you are plugging in the gearcase. As the engine sits higher, the pressure against the water inlets becomes lower (allowing the weight of the water in the engine block to cause a higher "head" pressure in the water supply tube and exhaust, which results in all or most of the water that might normally remain in the block being drained back into the lake, and leaving very little (if any) water in the block to help absorb the heat that is radiating from the block castings).
You can probably prove this yourself by observing the difference that 2" lower height will cause.
On a side note- and NOT saying this is the case, gasket leaks at locations such as the adapter plate or powerhead gaskets will exasperate this scenario significantly.