In the opening game the hosts scored five runs in the opening inning and added another five in the third frame.
Although the Mariners drove in a run in the third, fourth and fifth innings, they could not catch the Dragons, losing 13-3.
The second game of the day was even more one-sided with Richmond leading 6-0 after one and 18-0 after three, and despite Mariners pulling back one in the fourth, they lost in a game shortened by the mercy rule.
Mariners visit Guildford Mavericks for a single game on Sunday (11am).
Meanwhile Mariners ace pitcher Dickie Gofton has retired after 10 years with the club.
Gofton began with the original Medway Mariners and has been the team MVP on several occasions.
General Manager Simon Canter said: “Dicky has been there from the start and has been our MVP for more years than I can remember.
“There is no doubt in my mind that Dicky has to be the best pitcher I’ve seen at our level over the time I’ve been involved with the club.”