South Africa won by six wickets to increase their unassailable lead in the five-match series to 4-0.
The visitors put West Indies in to bat and restricted them to 231 for eight.
South Africa replied with 232 for four to win with 19 balls to spare but not before they slipped to 61 for three, leaving Prince and Kemp to right the innings with a stand of 132 for the fourth wicket.
Prince scored 89 not out off 117 balls with six fours, while Kemp's 65 came off 75 balls and included five fours and two sixes.
Shivnarine Chanderpaul [ Images ] top scored with 85 not out to anchor West Indies' total.
South Africa claimed the series when they won the third match by one run in Barbados on Wednesday, and the futility of Saturday's dead rubber was writ large amidst the West Indians' approach.
Chanderpaul's discipline, which saw him face 103 balls and hit five fours, was the exception.
Support for the West Indies captain was largely fleeting, and the biggest stand of the innings was the 50 shared by Chanderpaul and Ramnaresh Sarwan [ Images ] for the fourth wicket.
South Africa began their reply unsteadily when AB de Villiers [ Images ], Boeta Dippenaar and Jacques Kallis were dismissed for 17 runs each.
De Villiers and Kallis each advanced down the pitch and edged to Chris Gayle [ Images ] at first slip off fast bowlers Ian Bradshaw and Corey Collymore respectively.
Dippenaar slapped a legside delivery from Bradshaw to Xavier Marshall at square leg.
Prince and Kemp kept the runs trickling in but they survived several half-chances to break the partnership.
Marshall wasted a genuine opportunity to remove Kemp for 48 when, with the total on 169 for three, he stood on the midwicket boundary as he caught Kemp's pull to a delivery from off-spinner Gayle.
Kemp was awarded a six, instead, taking him to his half-century.
Prince and Kemp were separated in the 42nd over when Kemp top-edged a ball from Gayle to Sarwan at short point.
The last match in the series will be played at the same venue on Sunday.
C. Gayle c Prince b Ntini 3
X. Marshall c Prince b Ntini 3
R. Sarwan c Hall b Kallis 48
B. Lara c Prince b Nel 22
S. Chanderpaul not out 85
D. Bravo c Boucher b Ntini 28
D. Smith b Hall 13
C. Browne c Boucher b Langeveldt 11
I. Bradshaw c Prince b Langeveldt 6
F. Edwards not out 0
Extras (lb-2 nb-7 w-3) 12
Total (for 8 wickets, 50 overs) 231
Fall of wickets: 1-5, 2-16, 3-61, 4-111, 5-160, 6-180, 7-212, 8-230
Did not bat: C. Collymore
Bowling: Pollock 7 - 0 - 37 - 0 (nb-4, w-1), Ntini 8 - 1 - 34 - 3, Nel 10 - 2 - 42 - 1 (w-1), Langeveldt 8 - 0 - 42 - 2 (nb-2), Hall 9 - 0 - 42 - 1, Kallis 8 - 0 - 32 - 1
AB. de Villiers c Gayle b Bradshaw 17
B. Dippenaar c Marshall b Bradshaw 17
J. Kallis c Gayle b Collymore 17
A. Prince not out 89
J. Kemp c Sarwan b Gayle 65
M. Boucher not out 10
Extras (lb-1 nb-2 w-14) 17
Total (for 4 wickets, 46.5 overs) 232
Fall of wickets: 1-27, 2-36, 3-61, 4-193
Did not bat: S. Pollock, A. Hall, C. Lang eveldt, A. Nel, M. Ntini
Bowling Edwards 10 - 0 - 51 - 0 (w-1), Bradshaw 8 - 0 - 43 - 2, Collymore 8.5 - 1 - 30 - 1 (nb-1, w-1), Bravo 8 - 0 - 32 - 0 (w-2), Smith 7 - 0 - 44 - 0 (nb-1, w-1), Gayle 5 - 0 - 31 - 1 (w-1).
Result: South Africa won by 6 wickets