Kenneth Robeson 
Land of Long Juju [EPUB ebook] 

After Renny goes missing in Africa, Doc and his crew travel to the remote African kingdom, where they thwart a scheme by The Shimba to overthrow its rulers and loot its mineral wealth of rare red diamonds. Hastily rewritten to change the setting from Central America to Africa, hence the references to “four-inch-long vicious man-eating fish” (piranha) and other jarring incongruities.