When two boats share the same hull type — in this case both the Sylvan Mirage 818 F-SD 2008 and the Sylvan Mirage Fish 818 2012 are pontoon designs with aluminum construction — the buying decision usually comes down to a handful of practical questions: how many people are you putting on the water, how far do you trailer, and what does your tow vehicle weigh?
On paper these two are close siblings in the size department — Sylvan Mirage 818 F-SD 2008 at 18,0 ft versus Sylvan Mirage Fish 818 2012 at 18,8 ft. Weight tells a clearer story for trailering families: the Sylvan Mirage 818 F-SD 2008 tips the scales at 1 325 lbs — 1 170 lbs more than the Sylvan Mirage Fish 818 2012 at 155 lbs. That difference is meaningful if you're working within a half-ton or three-quarter-ton truck's tow rating, especially once you factor in a motor, gear, and fuel.
Both boats share a closely matched power ceiling — 50 hp for the Sylvan Mirage 818 F-SD 2008 and 50 hp for the Sylvan Mirage Fish 818 2012. Real-world performance will come down more to which motor is actually bolted on, its load at the time, and whether it's a 4-stroke or 2-stroke setup.
For family outings this is probably the sharpest distinction between the two. The Sylvan Mirage 818 F-SD 2008 is rated for 9 passengers, while the Sylvan Mirage Fish 818 2012 caps at 8. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Sylvan Mirage 818 F-SD 2008 could be the deciding factor.
Bottom line: Choose the Sylvan Mirage 818 F-SD 2008 if your priority is putting more people on the water — it handles 9 passengers and at 18,0 ft it has the deck room to back that rating up comfortably. The Sylvan Mirage Fish 818 2012 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 8 that costs less to run day-to-day.