When two boats share the same hull type — in this case both the Larson SEi 180 Fish Series O/B 2006 and the Larson Senza 186 I/O 2008 are modified vee designs with composite 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 — Larson SEi 180 Fish Series O/B 2006 at 17,0 ft versus Larson Senza 186 I/O 2008 at 18,0 ft. At 17 lbs and 27 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 Larson Senza 186 I/O 2008 tops out at 225 hp. Engine specs for the Larson SEi 180 Fish Series O/B 2006 aren't listed — confirm with a dealer before selecting an outboard.Fuel capacity breaks the other way: the Larson Senza 186 I/O 2008 carries 29 gallons versus 23 gallons in the Larson SEi 180 Fish Series O/B 2006. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
For family outings this is probably the sharpest distinction between the two. The Larson Senza 186 I/O 2008 is rated for 9 passengers, while the Larson SEi 180 Fish Series O/B 2006 caps at 6. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Larson Senza 186 I/O 2008 could be the deciding factor.
Bottom line: Choose the Larson Senza 186 I/O 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 Larson SEi 180 Fish Series O/B 2006 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 6 that costs less to run day-to-day.