A divorce between McLaren and Honda could be close, judging by the team bosses' criticism of the Japanese engine. But what are McLaren's options if it parts company with Honda? Adam Cooper gives his take on the possibilities.
Rumours that McLaren was considering a future without Honda first surfaced several months ago, but the situation is now beyond that stage, and it's no secret that the management of the Woking team has been actively seeking an alternative partner.
It's widely assumed that there will be a reunion of McLaren and Mercedes in 2018, and in many ways that is the logical and very obvious route. However, it seems that things are not yet set in stone. How could they be with the Honda deal still officially in place?
So perhaps there's a chance that instead, there could be an unexpected revival of another long forgotten F1 partnership – one involving McLaren and Alfa Romeo.
Zak Brown and Eric Boullier have both made it crystal clear that McLaren's patience with Honda has run out, and given the tone of their comments, the odds of the two parties still being together next year look slim.
That appeared to be the case even before a mind-numbingly frustrating Canadian GP, where Fernando Alonso was robbed of what would have been the team's first point of the year. The fact that the loss of a 10th place was received so poorly shows just where the team is at right now.
As Brown told Motorsport.com after the race, "we can't go on like this."
When the iconic partnership was renewed, it was accepted that it might take a season or three to become fully competitive – as in, challenging for podiums and knocking on the door of race wins.
The first year with Honda was a disaster, the second saw some upward momentum and justified optimism, and in 2017 things have clearly taken a turn for the worse. McLaren cannot afford to waste any more time.
Nobody in the Woking camp, and certainly not the team's major shareholders, goes racing just to make up the numbers.
But it's not just about egos. In F1 points mean prizes, and the further down the order you drop, and the longer you stay there, the less money you earn from the FOM pot – and having been ninth and then sixth in the past two seasons, the team is currently in last place, on zero points.
At the same time, poor performance on track does not impress sponsors, and several have migrated to other teams in recent years.
That double whammy puts a big dent in the positive contribution to the numbers made by Honda, and thus walking away from a lucrative works deal and paying hard cash for a competitive engine starts to make more sense.
McLaren is a team that should be winning, and it's hard to believe that the last title came in 2008, and the most recent victory in 2012. Reuniting with Honda was supposed to address that, recapture some of the magic of a past era, and crucially give the team an exclusive relationship with a major manufacturer, with all the resources that it can bring to the party.
It hasn't worked and it doesn't look like it will work any time soon, so it's time to move on, and find a shortcut to improved performance.
A divorce looks set to be messy, because this was obviously a complex, long-term deal involving huge sums of money. Honda is already committed to Sauber, so in theory it won't be pulling out of the sport in the way it did at the end of 2008, leaving Ross Brawn scrambling to save the Brackley outfit.
There's a supreme irony in the fact that what became Brawn GP was saved because works Mercedes team McLaren agreed that the Stuttgart manufacturer could bail out Brawn and co, with an engine supply – after then president Luca di Montezemolo had made a similar offer on behalf of Ferrari.
This was a generous gesture intended to keep the Brackley staff (and indeed Jenson Button and Rubens Barrichello) in gainful employment, but it backfired on McLaren when Brawn GP dominated the early part of the season, and Button won the world championship.
Liking what it saw, Mercedes decided to buy the team and make it its works outfit – at the ultimate expense of McLaren.
The major stumbling block at that time was the fact that McLaren was ramping up its road car ambitions, and there was an obvious clash with Mercedes, as it was becoming direct rival for those with a few hundred thousand to spend. Relations between Stuttgart and Ron Dennis became strained.
Against customer deal
McLaren eventually found itself downgraded to customer status, which is why Dennis began searching for a new partner – he was adamant that you cannot win in F1 as a customer team, despite Brawn having proven that it was possible, at least if you have an exceptional chassis.
By necessity, McLaren continued with Mercedes power after the Honda deal was signed, even into the first season of the new turbo V6 era. That inevitably increased tensions between the two, as Mercedes had obvious concerns about its IP.
At Suzuka in 2014, Dennis launched a tirade about the level of customer service from his long-time partner, focussing on a lack of access to "source code" that he felt would allow McLaren to enjoy the sort of advantage that the works team evidently had in qualifying trim.
Honda couldn't come soon enough.
"Even though you have the same brand of engine that does not mean you have the ability to optimise the engine," he said. "So you've got to start by putting yourself in a position where you have the best engine available.
"That's what we've done for the approaching years. We had a great partnership with Mercedes, but we intend to hit the ground running with Honda."
Less than three years later McLaren is in the bizarre scenario of trying to escape from Honda, and a return to Mercedes is its most obvious lifeline. The good news is that the two sides have a history together – the bad news is that history includes a lot of unhelpful baggage.
On the plus side, at engineering level the guys at Woking and Brixworth know each other well, and it's only been three years since the former built a car around the first version of the V6.
Mercedes has the capacity to supply a fourth team – it serviced Manor in 2016 – and next year the annual power unit allocation per driver drops to three per season, so that should mean that fewer resources are required per customer.
Marketing-wise, much could be made of a reunion between McLaren and Mercedes, if that suited both parties. However, that awkward clash of road car interests hasn't gone away, so perhaps there's an argument for a badging deal that also would give McLaren an extra package to sell to a sponsor.
But does Mercedes really want to have McLaren back on board? Not so long ago the top management refused to supply Red Bull, on the basis that having worked so hard to get into a winning position, why would it hand that advantage to a not very friendly rival?
One factor does work in McLaren's favour. There was a clash of personalities at the heart of the failed Red Bull/Mercedes deal, and it's probably fair to say that Christian Horner didn't have too many friends in Brackley or Stuttgart.
Crucially for McLaren, Dennis is now out of the picture, so much of the aforementioned baggage has been discarded. Brown, as he showed when he pulled off the Indy 500 deal, is a man people like to do business with, and who gets things done.
Nevertheless there are still some hurdles to overcome. You could argue that it might be better for McLaren to opt instead for Renault, and make a fresh start with a new partner.
Viry has a good reputation for providing parity, and for the moment at least, the works team is not a race winner, and thus that awkward element of competition doesn't come into the equation.
There's also the option to sell badging rights to the engine, as Red Bull has shown, which would help to pay the bills.
However, while Renault has made huge strides with its V6 over the past couple of years, it still lags behind its two main rivals.
Could Ferrari be an option?
It sounds crazy, not least because in marketing terms, those names don't fit for very obvious reasons – they are chasing the same wealthy customers.
However, McLaren could badge the Ferrari engine, just as Sauber did with Petronas for many years. And it might not have to be a TAG Heuer-type sponsorship deal. Consider the logos on the back of the works SF70H. What if McLaren could agree to run the Maranello engine with the Alfa Romeo name?
Sergio Marchionne has said that he wants to properly push the brand in F1, and this could be a brilliantly unexpected way to do it.
It would be especially appealing to him if McLaren pays $25m or whatever the price would be for the privilege of promoting Alfa Romeo, especially if Fernando Alonso could be part of the story too.
Even if Alfa doesn't fit, there are other brand names that could be used – although Chrysler doesn't have quite the same ring to it...
Remember that Ferrari loses Sauber next year, leaving just Haas as a customer, so logistically there is capacity.
The Mercedes is the engine everyone has coveted for the past three seasons, but the Ferrari is now right there. Why wouldn't McLaren want it, for purely competitive reasons, if all the other stuff can somehow be dealt with?
The obvious counter argument is that Ferrari has never supplied a truly competitive rival, and just as Mercedes had no wish to give Red Bull a helping hand, Maranello will be reluctant to hand over its technology to McLaren.
And could McLaren ever be 100 percent sure that it was getting parity of equipment – or in the words of Dennis, access to the "source code"?
Clearly, the marketing and competition issues would present a few hurdles. However, there's also the bigger picture of politics.
A lot is going to happen in the sport over the next few years as Liberty addresses both the future technical rules and, more controversially, F1's financial arrangements.
A marriage of convenience between Ferrari and McLaren would be pretty powerful, and potentially give Maranello some extra clout as it fights its corner. And the Mercedes voice would be correspondingly weaker.
Remember too that while Brown and Ferrari boss Maurizio Arrivabene would obviously be in the loop on any discussions, ultimately it would be agreed and sanctioned above their pay grades – between Marchionne on one side, and Mansour Ojjeh and the Bahraini royal family on the other.
That's pretty high-powered stuff, and if those guys are on the same page, anything is possible.
Think about what a great story it would be. A winning engine for McLaren puts a major player back in the game, and the sexy Alfa Romeo name makes a proper return to the sport – possibly with Fernando Alonso still in the picture.
Ross Brawn and Chase Carey would push like hell for it to happen. The FIA would also be keen for Ferrari to have three teams, rather than Mercedes (or Renault) expand to four.
There's even a little history for both sides to hang a positive story on. Back in 1970 Alfa Romeo sportscar driver Andrea de Adamich took a supply of the Italian marque's V8s to Bruce McLaren, who built a special M7D, and ran him as an extra works entry.
The package wasn't up to much, and even an upgrade to a newer M14D didn't help, and de Adamich didn't better an eighth place, achieved at Monza.
But the fact is that a McLaren-Alfa Romeo started four grands prix that year, and it remains a forgotten chapter in the history of both companies. Is there a chance that another may yet be written?