---

The purpose of a water separating filter is to get rid of water that might accumulate in the fuel tank. Water condenses and drips into a fuel tank when there is a temperature differential between cold tank walls and the surrounding warm ambient air. This is usually a winter condition when a "winter thaw" occurs.

The temperature of on deck tanks closely follows the surrounding air temperature, so no differential condensation can occur. Hence on deck tanks do not condense water out of the air and do not need the filter.

Conversely, built in tanks, and particularly those in foam insulated Whaler hulls, do not warm up quickly as the ambient surrounding air, and the moisture laden warming air enters the tank though the fixed 5/8" vent hose. with water likely condensing on the tank ceiling and walls, and dripping into the gasoline. Hence the need for a water separating filter. This is also the reason they tell you to fully fill your tank for the winter storage, so no tank "ceiling" is exposed, and hence no possible condensation can occur.

As we all know, Whaler has been only selling new boats fully rigged with Mercury outboards. Note that the smaller boats, that require on-deck tanks, are not fitted at the factory with water separating filters. Also note that all Whalers with built-in tanks are always (correctly) fitted with the filters. If you have on deck tanks, and feel you need a dirt filter, you can install a $5 in-hose plastic filter.