Regal LS4C Owner's Manual page 167

Zinc Anodes
zinc is a less noble metal, it will decompose
before other metals. Check these zinc anodes
periodically and have them replaced when they are
30% consumed. Notwithstanding, zinc is the most
popular metal used to protect parts that are exposed
to saltwater, freshwater or brackish water.
See the photos below for anode location on your
stern drive.
Zinc anodes in brackish or salt water need to be
checked more frequently. If the anodes seem to
be requiring frequent replacement there may be a
boat leaking DC current into the water taxing the
anodes. This is especially possible around a marina
environment. Contact a marine professional who
can measure the galvanic activity with a special
electrode and electric VOA meter. Refer to the
engine manufacturer's manual for exact anode
location and detailed information.
Inspect the ground leads for tightness if attached.
Note that parts damage due to galvanic or stray current
corrosion is not covered under warranty.
Sacrificial zinc anodes
are located on the drive
housing, trim tabs and/
or prop shaft to protect
softer metals exposed
to the water. Electrolysis
attacks the least noble
metals first. Because
167