On CNBC Wednesday, Former General Electric CEO Jack Welch knocked President Trump for his "crappy management practices" in handling FBI Director James Comey, but warned that impeaching Trump would "blow the market away."

Welch, who CNBC notes "has President Donald Trump's ear," discussed all the talk of impeaching Trump on CNBC's Squawk Box on Wednesday (video below). Though Welch admitted Trump made a "rookie mistake" in firing Comey the way he did, the former CEO largely defended his fellow businessman. But most notable of all Welch's statements was his warning about the potential impact of a Trump impeachment on the stock market.

Since Trump's electoral victory, the stock market has been booming, both the S&P 500 and Nasdaq closing at record highs earlier this week, while the Dow Jones is at a near record. Following a series of allegations against Trump over the last few days, the dollar index hit a seven-month low early Wednesday, while U.S. bonds sank and gold rose.

"An impeachment proceeding would blow the market away," Welch told CNBC.

Though Welch gave Trump a "D minus" for his management skills, Welch rated him highly on the economy and generally promoting the conservative agenda, saying, "I think without question we have a guy that's on the right agenda with crappy management practices."

While Welch wouldn't specifically comment on Trump's alleged attempt to influence the FBI investigation into former adviser Michael Flynn, he did weigh in on Trump's treatment of Comey. Trump, said Welch, wasn't going to "make any friends" by handling situations like he handled the firing of Comey. Trump, said the former CEO, should have treated Comey as kindly on his way out as he did when the new president first came into office.

As for his priorities now, Welch suggested Trump needs to focus on uniting his administration and the Republican Party.

Though Welch didn't shy away from faulting Trump on his "management practices," he also highlighted some of the president's key successes thus far, giving Trump an "A" on improving the overall "confidence" of American businesses and on his Cabinet and Supreme Court choices.

Partial transcript via CNBC.