Since Hummer was owned by General Motors, its motor was a GM-made.
No, the H3 was discontinued in May 2010.
H3 has 4 engine options, with horsepower of 223 hp, 245 hp, 305 hp and 242 hp.
Hummer H3 was available with a 3.5i 20V (223 hp), 3.7i 20V (245 hp) and a 3.7i 20V (242 hp).