The three-time grand prix winner achieved his success with Williams, but he says it “hurts” to see McLaren suffering with its Honda power at present.
“If you like formula one, it hurts to see where they are,” Boutsen told the Dutch publication Formule 1.
“But Stoffel must persevere. As a driver you have to block out the rear view mirror because you have to always look ahead,” said Boutsen, who is now 60.
“He still has time. He’s only 25 and my first victory also took time. But I knew from the start ‘Give me a good car and you’ll hear the Belgian anthem’,” he added.
“So he must have patience. From what I saw in the lower classes I can say confidently that Stoffel has the potential to be world champion.”
Boutsen said Vandoorne’s place on the grid is already a testament to his talent, given the difficulty for Belgians to break into top-level motor racing.
“For Belgians it is so much harder to get to F1,” he confirmed.
“Belgium has no big sponsors, so you have to do it all alone. I know it well, as at Williams I was better than my teammate Riccardo Patrese but as an Italian he was commercially more interesting.
“And another sponsor, Labatt, wanted a driver for the British market, which was Nigel Mansell. As a Belgian you always have to show more than an Englishman, Italian or German,” Boutsen insisted.