Considering its current definition (see below) and the wish to be politically correct, I wonder whether the word has come to acquire any racist overtone.
What is a coal miner hewer-Ask.com. Coal miner hewer is a person who hews or cuts the coal from its natural situation. The hewer is the actual coal-digger removing it from the coal face.
The mower is probably consuming far more gasoline than it should during operations. Black smoke is also an indicator that oil has found its way into the cylinder, and the mower is trying to burn it along with the fuel. In some cases, the mower will not restart.