That's not actually how it works for me. The google custom search is for the forum only so I get that as an option when I'm in the forum, however, everywhere else (homepage, articles, wiki, etc) it gives the normal built-in search as the only option. The Google custom search is based on the forum, so that's the only place it will work.
Wild Love Brewing
Brew Stats | Brewlog | Fermentation chamber
Drinking: Late for Breakfast Stout, How Rye Am I? Saison, HD 2013, Graff
Bottle conditioning: Nut Brown Ale, EdWort's Hause Pale Ale
Primaries: Dry Irish Stoat, Oatish