What is the weight difference between 100 hp and 150 hp Continental engine?
Which variants are you specifically talking about?

The Continental O-200-A (100hp) weighs 170.18 lb (77.19 kg) dry, without accessories.

I can't find a 150hp Continental, so here is the closest variant I could find:


Continental O-300 (145hp) weighs 268 lbs (121.5 kg) dry, without starter or generator
The O-300 is also listed as a C-145 and as a C-175
E165-2 165 hp dry weight 351 lb (159 kg) - Variant of the O-470
E165-3 165 hp  dry weight 352 lb (160 kg) - Varian of the O-470


I hope that's what you were looking for.