I copied some summaries of Wilbur's books (from amazon, britishempire.co.uk, wikipedia and wilbursmithbooks.com) and put them together here. I hope it refreshes somebody's memory.
The Dark of the Sun (1965)
Bruce Curry sets out with a trainload of mercenaries to relieve a mining town in the heart of the African jungle although they are more interested in the diamonds to be found there. Either way the journey turns out to be a nightmare.
Timeframe: 1960s (Congo Crisis)
Shout at the Devil (1968)
As World War One approaches Anglo-German rivalry between an ivory hunter and the German Commissioner becomes all too real as the two sides go head to head. The arrival of a German Cruiser in the area turns this backwater into a strategically important target - if only they can find that ship.
Timeframe: 1913 - 1915 (World War I)
Gold Mine (aka Gold) (1970)
Rod Ironsides, ambitious and hard-living mining expert, knows that the general managership of the Sonder Ditch gold mine is the chance of a lifetime. But the price of unquestioning obedience to the coldly obsessive genius of Dr Manfred Steyner proves impossible to pay. Both men are but unwitting tools of powerful people - for whom the control of a gold mine is only part of the realization of dreams and ambitions which include the destruction of the very mine itself . . .
Timeframe: 1960s
The Diamond Hunters (1971)
The Van Der Byl Diamond Company, willed by its founder to his son Benedict, his sister Tracey and their estranged foster-brother Johnny Lance turns out to be a bequest of hatred. For it is couched in such terms as to offer Benedict the instrument of destruction of his bitterest rival. 'Destroy Johnny' is the old man's implacable message. And so, consumed with envy for Johnny, Benedict sets out in ruthless pursuit of this goal – and Johnny is plunged into a maelstrom of greed, vengeance and murder . . .
Timeframe: Late 1960s
The Sunbird (1972)
A hazy aerial photograph and a sinister curse are the only clues Dr. Ben Kazin has before he stumbles on the archaeological discovery of a lifetime. Beneath the red cliffs of Botswanaland a magnificent unknown civilization has remained buried for millennia. But the magic of uncovering a lost culture is harshly interrupted by the violence of terrorists, love, intrigue and the breathtaking secrets of centuries.
Timeframe: Modern Times / Ancient Times
Eagle in the Sky (1974)
Drawn to the sky as though to his natural element, young David Morgan spurns the boardroom future mapped out for him by his family for the life of a jet pilot. Then he meets Debra, the beautiful Israeli writer for whom he will fight, in another country's war, at the controls of his Mirage. Yet the breathless action which brings them together is also the very tragedy that will threaten to tear them apart. . .
Timeframe: Modern Times
The Eye of the Tiger (1975)
Harry Fletcher, a man with a chequered past, has reformed and is making an honest living as a charter skipper fishing for big game in the seductive waters of the Indian Ocean. Suddenly men from the world of violence Harry has put behind him overturn his good intentions, involving him in a hectic race to recover a fabulous treasure from an ancient wreck.
Timeframe: Modern Times
Cry Wolf (1976)
A European and American gun runner become involved in gun running in the Abyssinian conflict of 1935-6. The Italian armies are going to make life as difficult as possible for these entrepreneurs.
Timeframe: 1935 - 1936 (immediate before World War II)
Hungry as the Sea (1978)
Robbed of his wife and ousted from his huge shipping empire, Nick Berg is hell-bent on vengeance. It is the sea which gives him his opportunity. When his arch-rival's luxury liner is trapped in the tempestuous Antarctic, Nick stakes all to pit his powerful salvage tug, the Warlock, in a desperate race against time and the elements . . .
Timeframe: Modern Times
Wild Justice (aka The Delta Decision) (1979)
The hijacking of a jumbo jet off the Seychelles galvanises anti-terrorist chief Peter Stride into the action for which he has spent a lifetime training. But even in the hail of bullets which follows, he knows that this is only the beginning of a nightmare. Stride is the one man who might find the twisted genius who holds the world hostage – if only his every move were not anticipated by the enemy...
Timeframe: Modern Times
Elephant Song (1991)
In the blinding light of Zimbabwe's Chiwewe National Park, Dr Daniel Armstrong, world-famous TV naturalist, films the slaughter of a herd of elephant. In London, anthropologist Kelly Kinnear is forced into violent confrontation with the shareholders of the most powerful conglomerate in the City of London, warning them of the destruction of an African country. Now the time has come to act. Together, Armstrong and Kinnear forge a passionate alliance - and begin the fight against the forces of greed, evil and corruption attacking a land they would both give their lives to save..
Timeframe: Modern Times