The E-185 was rated at 185hp at 2300rpm, and 205 at 2600rpm takeoff. It is about 215-220 at 2900rpm where most airboaters run them. The power is real close to a gpu, they use the same pistons cam lobe profiles but arte dual plug with a better intake system. The factory claimed weights are 343lbs. on the dry sump model, 352lbs. on the wet sump model, so they are a light 6 cylinder which is why you are seeing more being used in raceboats.
They also have an E-225 which has a more aggressive cam and bigger carb on it, I have seen people use this cam in E-185's and GPU's with good results, usually about 30hp gain. They can also be upgraded with angle valve 470 and 520 cylinders for more power, but adds about 60lbs to the motor. I have a friend that just got a Davis raceboat with a built E-225 that runs really well using the straight valve cylinders. It is a real nice motor IMHO, I would have built one if I didn't get such a good deal on my io470.
Larry