Is my propeller too large?

If too large the propeller will absorb the hp too early and hold the RPM down, causing the engine to “lug”, not reaching the specified RPM resulting in “over propping”.   The thrust generated will be without the desired torque from full hp and could possibly damage the engine from unburnt fuel, evidenced by excessive black smoke at the exhaust as the engine cannot get to the given RPM for the amount of fuel it is receiving. This is not good for the cylinder walls and in the case of new electronic controlled engines could possibly shut them down.