i have a 1988 steigercraft with a volvo penta aq211a 290 outdrive that is working perfectly, i use the boat on weekends in salt water and its left in the water, original motor and outdrive and boat is never abused, always run around 3000 rpm, whats the life expectancy of a 290 outdrive and what would i replace it with when the time comes, i have been looking for replacement 290 for backup incase something happens to mine but their hard to find , what would be my options???? im thinking ahead here!