It is essential to be rowing specific, hence the core weights are:
On top of that, you have to exercise the Antagonists to maintain balance, such as:
You can be innovative with these and it is good to mix it up sometimes. For the Chin Ups, Abs, Press Ups and Dips you need to do more reps than for the other exercises (approx. 15-25).
The weights workout should take about an hour (to start off), but if you really want to see some results it can take about 2.5 hours. As you decrease the reps you obviously increase the weight. Don't take too much time for each set, but put on enough weight that you can barely lift the last rep.
3 sets of 12 reps of the Core Weights, plus as many Antagonist Exercises as you like or you have time for.
4 sets of 10 reps Core Weights, plus Antagonists
5 sets of 8 reps Core Weights, plus Antagonists