When two boats share the same hull type — in this case both the Mariah FS18 2009 and the Mariah R18.9 2010 are modified vee designs with fiberglass 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 — Mariah FS18 2009 at 18,0 ft versus Mariah R18.9 2010 at 18,3 ft. At 31 lbs and 33 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 power gap is worth calling out. Rated to 225 hp, the Mariah R18.9 2010 has a 35-hp advantage over the Mariah FS18 2009's 190-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Both carry nearly identical fuel loads — 22 gal and 22 gal — so range won't be a tiebreaker here.
Both boats are rated for 8 passengers — a good fit for a family of four or five plus guests. Comfort at capacity is another matter; the longer hull typically means more seat options and better weight distribution.
Bottom line: Performance buyers should lean toward the Mariah R18.9 2010 and its 225-hp ceiling. If fuel economy and quieter running matter more than top-end speed, the Mariah FS18 2009 with its 190-hp rating is the more economical daily driver.