1998+ Mercury Mariner 25HP Bigfoot Service Manual, Page 408Get this manual
LOWER UNIT
Trim Tab Adjustment and Replacement
IMPORTANT: The trim tab is made of special alloy to aid in protecting the drive shaft housing and gear housing from galvanic corrosion (corrosion and pitting of metal surfaces)Do not paint or place protective coating on the trim tab, or trim tab corrosion protection function will be lost