McLaren: Honda F1 engine swap was needed to avert 'proper disaster'

The team joined forces with the Japanese engine manufacturer in 2015 with the aim of reviving the success the partnership achieved in the late 1980s and early '90s.

But the partnership has failed to deliver anything close to the expected results over the past three seasons.

McLaren finished ninth in the constructors' championship in 2015, sixth in 2016 and is currently ninth in this year's standings.

The two parties formally announced they would part ways at the end of 2017 last week.

"When you look at the last three years it's been a proper disaster for us in terms of credibility and getting new sponsors," said Boullier in an interview with the official F1 website.

"And then you have to take the long-term view: 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.

"We are ninth in the championship - with a top engine I think we would be fourth right now and just on the FOM money we could cover the engine side, so it will not be a big risk on the monetary side.

"Thanks to the shareholders who have been brave enough to take a sporting choice and not hurt McLaren. They could have said, 'Let's wait until Honda wakes up'."

Boullier revealed McLaren began considering the future of its partnership with Honda as early as pre-season testing before the 2017 campaign, when it was clear that the Japanese engine had failed to deliver the performance the McLaren expected.

"The crucial moment was after the Barcelona testing, when we tried to work and help Honda to improve the situation in a very short time, including having discussions with the other engine manufacturers," he said, "and without going into details, it became obvious that they again would miss the target that we had agreed for the season.

"Then by the summer we knew that we had to take a decision, to stay or not to stay.

"I can't say a date, but there had been a couple of targets missed by summer."

Despite the lack of results, Boullier conceded parting with Honda had not been an easy decision to make.

"On paper everything looked right. Just the way it's been done was not right, obviously.

"Luckily we managed to make it an amicable settlement and they understood that all the investment that they have made, they should get a reward from that at some stage.

"We can't wait - but they can get the reward with somebody else.

"I am so glad that they have decided to stay in Formula 1 and commit to another team.

"Personally I feel a bit sad that it didn't work, but these have been [a] very intense three years."