The Bertram 31 Flybridge Cruiser 1974 vs Bertram 37 Convertible 1987 comparison sits squarely in the category of decisions where specs alone won't tell the whole story — intended use, storage, and long-term ownership costs all factor in.
The power gap is worth calling out. Rated to 375 hp, the Bertram 37 Convertible 1987 has a 235-hp advantage over the Bertram 31 Flybridge Cruiser 1974's 140-hp ceiling — enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Bertram 31 Flybridge Cruiser 1974 carries 225 gallons versus 47 gallons in the Bertram 37 Convertible 1987. 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 Bertram 37 Convertible 1987 is rated for 11 passengers, while the Bertram 31 Flybridge Cruiser 1974 caps at 9. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Bertram 37 Convertible 1987 could be the deciding factor.
Bottom line: Choose the Bertram 37 Convertible 1987 if your priority is putting more people on the water — it handles 11 passengers and at 37,0 ft it has the deck room to back that rating up comfortably. The Bertram 31 Flybridge Cruiser 1974 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 9 that costs less to run day-to-day.