London - The last three years with Honda have been a "proper disaster" for McLaren's image but a new deal with Renault will revive the Formula One team's fortunes, according to racing director Eric Boullier.
The former championship-winning team announced last week that it was ending the relationship with Honda and starting afresh with the French engines from the 2018 season.
McLaren, which was dominant with Honda in the late 1980s and early 1990s, is currently ninth of 10 teams in the championship and has not won a race since 2012, when it had Mercedes power.
"When you look at the last three years it's been a proper disaster for us in terms of credibility and getting new sponsors," Boullier told the official Formula One website (www.formula1.com).
Could take years to bounce back
"In the next five years I am absolutely sure that we will go back to where McLaren belongs. And with this bouncing back we get our credibility back and it will rebuild our sponsor portfolio.
"It might take two to three years," he added.
The teams' share of revenues is distributed on a sliding scale relating to their championship position over a number of seasons, as well as fixed payments to top teams like McLaren for historical performance.
Boullier said McLaren's shareholders - Bahrain's Mumtalakat holding company and Saudi-born businessman Mansour Ojjeh - had been brave to take a sporting choice "and not hurt McLaren."
"They could have said, 'Let's wait until Honda wakes up'," added the Frenchman.
The decision to split followed a number of missed targets but Boullier said a crucial moment came after pre-season testing when it became clear that Honda was off the pace.
Honda motorsport head Masashi Yamamoto, whose company will move to Red Bull-owned Toro Rosso, has accused McLaren of being a 'systematic' company that can find change hard to deal with.
Boullier denied that the two had been 'talking past each other' but said that he sometimes acted as peacemaker to help bridge the culture gap. He recognised the separation had not been easy.
"The whole story for them, as it was for us, was to recreate the legacy of the past. On paper everything looked right. Just the way it's been done was not right," he said.
"We can't wait - but they (Honda) can get the reward with somebody else. I am so glad that they have decided to stay in Formula One and commit to another team."