Their match at OTs & Romsey cancelled, Portsmouth loaded four of their table topping Southern Premier Division 1 team into their seconds, with Harry Gadd, the former Havant skipper, hitting 174.
Dan Wimble hit 73, Sujeeth Danni 31and Hampshire U18 spinner Charlie Collins 59.
First team opening bowler Joe Kooner-Evans took two wickets as Hythe were dismissed for 98 to lose by 270 runs.