46 CFR §169.608

1. (a)Hull penetrations for non-integral keel cooler installations must be made through a cofferdam or at a sea chest.
2. (b)Non-integral keel coolers must be suitably protected against damage from debris and grounding by recessing the unit into the hull or by the placement of protective guards.
3. (c)Each non-integral keel cooler hull penetration must be equipped with a shutoff valve.