Saltwater and brackish water corrosion has been chewing up stern drives ever since Volvo Penta unveiled the species back in the late 50´s. Then not long ago Volvo Penta introduced its Ocean Drive, essentially a stainless steel skeleton clad in a tough as nails, non corrosive composite shell. Now MerCruiser has introduced yet another option to be forever more known as SeaCore. Like the man said, a little competition is a good thing.
Simply put, SeaCore is super-corrosion-resistant stern drive that´s specifically engineered to thrive in conditions that would rapidly consume mere aluminum. SeaCore is a package including both the engine and the drive. No big surprise, both the engine and drive are liberally endowed with stainless steel fasteners and other components, plus standard closed cooling with long-life anti-freeze and an integrated freshwater flush port that connects to a garden hose to purge salt crystals and other mineral junk from the cooling passages. Castings exposed to saltwater are hard anodized XK360, a low-copper aluminum alloy.
But it is the sum and substance of the drive leg that´s the most compelling story of all. Its castings are industrial hardcoat anodized, a process that converts basic aluminum into a hard, inert layer of aluminum oxide. Aluminum oxide, tougher than case hardening, is second in hardness only to industrial black diamonds. Did I mention the surface is hard? But even more important, the non-conductive surface pulls the plug on galvanic corrosion. At the molecular level, if no current flows, corrosion does not exist.
That hard, inert, abrasion resistant, anodized surface is next treated with a metal-ion sealing solution further enhancing corrosion resistance. Then an electrostatically-carried epoxy coating is applied. While epoxy is an effective barrier to environmental influences (water and salt), ultra-violet rays rapidly destroy it. So as a final measure component parts are primed and then painted with ultra high quality UV resistant, baked enamel. Besides external surfaces, internal water jackets and exhaust passages are hard anodized.
Unless your boat is a hangar queen, inevitably you'll scratch the drive. With a Seacore drive leg it's no big deal. Damage doesn't travel below the surface because the surface is an integral part of the material. Therefore, repairing a flaw in the paint job paint means following established practice and procedure. So scrub the surface, then prime and topcoat.