When two boats share the same hull type — in this case both the Zodiac Pro 500 2010 and the Zodiac Pro Open 550 2008 are inflatable rigid 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 — Zodiac Pro 500 2010 at 15,4 ft versus Zodiac Pro Open 550 2008 at 18,0 ft. Weight tells a clearer story for trailering families: the Zodiac Pro 500 2010 tips the scales at 507 lbs — 410 lbs more than the Zodiac Pro Open 550 2008 at 97 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.
The power gap is worth calling out. Rated to 120 hp, the Zodiac Pro Open 550 2008 has a 50-hp advantage over the Zodiac Pro 500 2010's 70-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load.
For family outings this is probably the sharpest distinction between the two. The Zodiac Pro Open 550 2008 is rated for 11 passengers, while the Zodiac Pro 500 2010 caps at 9. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Zodiac Pro Open 550 2008 could be the deciding factor.
At this size, power-to-weight ratio matters more than outright horsepower. The Zodiac Pro Open 550 2008 comes in at 1 lbs per hp versus 7 lbs per hp for the Zodiac Pro 500 2010. The lower the ratio the more explosive the acceleration — meaningful on a short RIB where bursts of speed, quick planing, and agility in surf or tight waterways define the experience.
Top speed is rated at 45 mph for the Zodiac Pro Open 550 2008 and 41 mph for the Zodiac Pro 500 2010.
Bottom line: Choose the Zodiac Pro Open 550 2008 if your priority is putting more people on the water — it handles 11 passengers and at 18,0 ft it has the deck room to back that rating up comfortably. The Zodiac Pro 500 2010 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 9 that costs less to run day-to-day.