The problem with the PT apears to be towing capacity (1,000 lbs), not
the 4 cylinder engine. The PT Cruiser Turbocharged GT has more
horsepower than most V6 pickup trucks. The 4 Cylinder PT Cruiser has
practically the same HP as the Ford's F-150 V8... that's V-EIGHT, not
V-SIX !!!
Ford F-150 with a 4.6 L V8 has 231 HP
PT Cruiser GT with a 2.4 L 4 cylinder has 230 HP

The F-150 has more torque (293 vs 245), but the PT Cruiser GT still
beats the torque of most 6 cylinder pickups, including the Ford Ranger
with it's upgraded 4 liter V6.

Torque comparison (from Edmunds.com):
Ford Ranger 3 liter V6 - 180 lb-ft @ 3950 RPM
Jeep Wrangler 4 liter inline 6 - 235 lb-ft @ 3200 RPM
Dodge Durango 3.7 liter V6 - 235 ft-lb @ 4000 RPM
Ford Ranger 4 liter V6 - 238 ft-lb @ 3000 RPM
PT Cruiser GT 4 Cylinder 2.4 liter Turbo - 245 ft-lb @ 2800 RPM
Ford F-150 8 Cylinder V-8 4.6 liter - 293 ft-lb @ 3500 RPM

I still don't think the PT would be good for towing a big boat, but
don't assume 4 cylinder means low power.