Just brought a 13hp Nick home a few weeks ago, another boiler project. Anyway, ran it across the scales and she weighed in around 12,500, give or take a little bit. I had another boiler on the trailer and guessed its weight, that is why I don't have an exact weight on the Nick engine. Regardless, it should bring you in the ball park for the 15hp. I believe they are comparible in stature.