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Marine Engine Digest |
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Home - more engine profiles - diy engine repairs - special reports Mercruiser sea core: solving stern drive corrosion problems
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Saltwater and brackish water corrosion has been chewing up stern drives ever since Volvo Penta unveiled the species back in the late 50īs. 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 Mercury Marine has introduced yet another option to be forever more known as MerCruiser SeaCore. Like the man said, a little competition is a good thing.
MerCruiser SeaCore 496 Magnum HO with Bravo 3 stern drive.
Simply put, Mercruiser SeaCore is super-corrosion-resistant stern drive that was specifically engineered to thrive in conditions that would rapidly consume mere aluminum. MerCruiser SeaCore is a package including both the engine and the drive. No big surpise, 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 thatīs 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 industrail 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 currrent flows, corrosion does not exist.
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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 youīll scratch the drive. With a Seacore drive leg itīs no big deal. Damage doesnīt 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.
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