Originally Posted by Scout 30
Technically filling your day tank is not considered to be polishing. With polishing you would typically pump your fuel through your filter at a relatively high pressure for several hours, often on a timer but not necessarily. If you don't return to the same tank you are drawing from the tank you are sending the fuel to will overflow through the vent. When filling your day tank you would monitor
the tank & turn the pump off before it's full. If you leave the pump on for the day tank it will also overflow through the vent unless you have an overflow valve that prevents this from happening.
Thus why having the day tank overfill into the keel tank is how we designed it.
Polishing the fuel back into the keel tank is fine, but we wanted to ensure the day tank always had clean and fresh fuel to the engine
algae or sediment caked filters is far easier when you have the time to do so, not when having to motor
down a busy ship channel. The day tank essentially has a fitting on the top that allows excess fuel in that tank to gravity feed back to the keel tank.
If the polishing filters get clogged, then we don't lose the engine
, just shut the pump down when the pressure gets too high, clean it at leisure, then start pumping again, and the engine never has to be shutdown in the process unless the day tank runs dry before switching the filters.
Having had two occasions in my lifetime that scared the crud out of me from bad fuel clogging the main filters and shutting the engine down at the last opportune time, it seemed a better way than just having dual selected filtration. Can keep and store more fuel on board for a longer period of time.