When two boats share the same hull type — in this case both the SunChaser 8520 4.0 2009 and the SunChaser Oasis 818 Fish 2013 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?
Size is the most obvious dividing line here. The SunChaser Oasis 818 Fish 2013 measures 18,1 feet overall (2013), giving it roughly 16,1 additional feet of deck space compared to the SunChaser 8520 4.0 2009 at 2,0 feet (2009). At 185 lbs and 155 lbs respectively, both sit in a similar weight class — either should pair comfortably with most mid-size SUVs and half-ton trucks, though always confirm your specific tow rating with the motor added.
The SunChaser Oasis 818 Fish 2013 tops out at 50 hp. Engine specs for the SunChaser 8520 4.0 2009 aren't listed — confirm with a dealer before selecting an outboard.
For family outings this is probably the sharpest distinction between the two. The SunChaser 8520 4.0 2009 is rated for 12 passengers, while the SunChaser Oasis 818 Fish 2013 caps at 8. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the SunChaser 8520 4.0 2009 could be the deciding factor.
Bottom line: Choose the SunChaser 8520 4.0 2009 if your priority is putting more people on the water — it handles 12 passengers and at 2,0 ft it has the deck room to back that rating up comfortably. The SunChaser Oasis 818 Fish 2013 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 8 that costs less to run day-to-day.