Originally Posted by
Tim Kurcz
Most outboard rods are forged steel, copper plated (carburize mask), rough machined (removes copper plate from intended surfaces), assembled, carburized, then finish machined (ground/honed). Copper plated areas are soft, only the bearing/wearing surfaces are hardened. To prove this to yourself, clamp a spare rod in a vice, apply torsion with a pipe wrench, and watch it twist without shattering.
For the proto rod, copper will be removed from the cap, the extension blade tig welded in place with the rod assembled and fully torqued. Following, the journal bore will be honed round and to size, and the pivot bore will be machined.
After swing fitting, the proto rod and cap bearing surfaces will be Brinnell tested. If there is no significant difference, the 888 might be run with welded rods. If the difference is unacceptable, custom rod caps will be machined, and the bearing surface will be carburized, honed, etc.
Side note: It might surprise you to know that mod outboard racers have been honing .002" - .0025" from the big end bores for many years. This procedure followed Mercury's change from .880" to .882" crank pins. It allowed rods to survive race conditions without overheating (bluing).
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