The 71-year-old completed the 26.2mile course some two minutes quicker than his previous best time.
Ratcliffe, who has a 27.7% stake in United, then set off for Wembley to watch his side in their FA Cup semi-final clash against Coventry.
The winners of that tie will take on holders Manchester City in the final on May 25th.
And, while Ratcliffe says his side would be underdogs, he says United are putting the building blocks in place to become top dogs in the city once more.
‘About four and a half (hours), something like that,’ Ratcliffe told the BBC after finishing the course.
‘At my age that’s probably okay. I’ve got to be quick, I need to be there (Wembley) at half-time. Man City are in the final again, it would be great (to reach the final). We would definitely be the underdogs. Not for long, though!
‘There are some parallels (between marathon running and football), I have to say, but it just requires some grit. Always in a marathon after 30k it gets difficult and I don’t think we are at 30k with football yet.’
United have appointed Omar Berrada as the club’s new CEO, while former Man City director Jason Wilcox has joined from Southampton as technical director.
But United must wait for Dan Ashworth to serve gardening leave at Newcastle, unless they meet the Magpies’ £15m valuation.
‘With football, you get these new really capable people to come into the team but they are all on gardening leave so it takes months to bring people in. It’s a real issue,’ said Ratcliffe.
‘They can’t work for us and the fans are impatient. Whether people like it or not, they have to be patient. You can’t just turn it around, it takes time.’
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