Flush out the engine at home after every outing. This doesn't just apply to saltwater adventures, but to the fresh water outings as well.
Your outboard motor is usually designed and manufactured to precise specifications to ensure years of trouble-free operation. This includes the fuel system.
Compared to the outboard motors of years ago, today's outboards are very reliable; however they still require some maintenance to keep them running at their best.
While bad fuel and a dead battery remain the primary reasons, a modern outboard might leave you in the lurch, another area that deserves your frequent mechanical attention is the propeller shaft.