They use ALL of the output. If something is not perfect, the engine will show it more emphatically than the large engines having a lot of excess horsepower. Selection of the replacement bearing is important. Use either a grade 3 or 5 bearings, so that you have tolerances that are correct. If you buy your bearings from Boca Bearings , you can't go wrong.
Ceramics also offer the correct fit and longevity.
You should look at this option also. I like to remove all oil from the bearing to be installed, so that there is nothing to burn if temps are high in the replacement process. Probably doesn't really hurt anything, but the bearing doesn't roll very well with the gum in it. I like to use Boca s Midas Touch Lubricant to assemble the engine. It has Teflon platelets that really seem to protect the engine at startup.