SECTION 2
ILMOR ONE-DRIVE OWNER’S MANUAL
2-4
© 6/2016 Ilmor Marine Engines, Version 1.0
CORROSION PROTECTION
Galvanic Corrosion
Galvanic corrosion results whenever two or more dissimilar metals (like
those found on the stern-drive) are submerged in a conductive solution,
such as saltwater, polluted water or water with a high mineral content
because a chemical reaction takes place causing electrical current to flow
between the metals. The electrical current flow causes the metal that is
most chemically active, or anodic, to erode. If not controlled, galvanic
corrosion may corrode stern-drive components.
NOTICE: The anode of the stern-drive is only calculated for the stern-
drive. Changing the material of the propeller may require additional
anodes to be installed on the stern-drive.
Corrosion Control
It is the boat designer’s responsibility and/or the re-powering engineer’s
responsibility to design the proper systems and equipment to control and
reduce the possibility of galvanic corrosion.
To help control the effects of galvanic corrosion, Ilmor Marine One-Drive
stern-drives come with several anodes and an electronic anticorrosion
system (I-CaPS) that protect the stern-drive in moderate corrosive
conditions. However, it is essential that the owner/operator frequently
monitor the anodes for wear, inspect the stern drive for corrosion and
replace the anodes often enough to provide a sacrificial surface for the
electrical current to attack. Galvanic isolators are also available from
the aftermarket (not supplied by Ilmor) to block stray current while still
providing a path to ground for dangerous shock currents.
The rate of corrosion depends on numerous factors, such as:
• The number, size and location of anodes on the stern-drive and vessel;
• The marina environment such as stray current in the water, fresh or salt
water and use and isolation of shore power;
• Improper application of marine paint or antifouling paint;
• Failure to repaint damaged areas; and
• How the vessel is bonded.
Please check with the boat builder, dealer or other professional to
determine if your vessel and/or stern drive is adequately protected from
galvanic corrosion.
If anodes erode quickly or if signs of corrosion are evident, the owner
should take immediate corrective action. Ilmor recommends consulting
an engineer specializing in marine electricity and corrosion control to
determine the best way to correct the rapid erosion of the anodes.
