We did our deck in 5/4 mahogany (cambera?) with a Sikkens Cetol SRD finish and 10 years in it's still looking good. First few seasons it really soaks up the finish but it's at the most every other year since. Very unstable wood though, keep it out of the sun until finished and be sure to seal the end grain with wax.
Ipe seems to be a good choice as well but is harder to work with from what I've heard.
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