After 15 years or so of thinking no other author can match Wilbur Smith's standard of adventure writing I think I've found another favourite. I picked up a copy of Passage to Mutiny by Alexander Kent in January, and if you are a fan of the nautical Courtneys then I don't think you'd be disappointed with this. The principal character is Richard Bolitho, and the books follow his career in the Royal Navy.
I've never really got into Jack Higgins or Patrick O'Brien, tolerated Peter Watt (am currently reading Shadow of the Osprey) and I quite like Gerald Seymour, but this is the first time I've been gripped as much as WS. More here:
http://en.wikipedia.org/wiki/Richard_Bolitho