I've had posted a similar question last year but here goes.

2006 F12X with about 67 hours on it. Oil was changed fall 2011 and only put a few hours on it last year, had my mechanic flush with anti-freeze, and only ran it for the length of time it took to burn a tank and a quarter of fuel this year. Should I just flush it with anti-freeze myself this year? I used to flush my two-stroke Sea Doo with a hose, gravity, a funnel, and anti-freeze. Is it that simple on a four stroke? The oil is two years old but it is synthetic and can't have more than ten to twelve hours on it. Very similar situation with my 2008 Yamaha VX Cruiser. Worth having oil changed? Waste of money? Just flush with anti-freeze, throw it on a tender, and hope to use it more next year?