More than 20 people signed up to the organ donor register at an awareness-raising event.
Watch manager Stu Vince, from Eastleigh, and firefighter Phil Jackson, of Cosham fire station, were at the Nuffield Health and Wellbeing Centre, Northern Parade, Portsmouth, encouraging people to sign up.
The event saw 25 people sign up and more than 100 take registration forms away.
The pair are running from Portsmouth’s Queen Alexandra Hospital to Land’s End – clocking up an average of 26 miles a day.
Then they will row back from Penzance to Gunwharf Quays.
The challenge starts on May 20.
The aim is to encourage more people to become organ donors and raise money for Portsmouth and Southampton hospitals.
The challenge has been inspired by Stu after he donated one of his kidneys to family friend Michael Paxman, aged 20.
To find out more, or to donate money, visit thebigdonorchallenge.co.uk.