First you have to make sure you train on a Concept 2 machine. These have been designed specifically for rowing.
go check http://www.concept2.com/us/training/technique.asp
Try to find your pace: typically 20-22 stroke per minute for which you could row hours. Then with that same rhythm try to increase the strength.
I've even done a half marathon once
at 2min / 500m
The day you want to drain yourself out you accelerate the pace and increase the the strength. It's tough to reach the same number of stroke per minute on a rowing machine compare to what you could reach in a eight. But don't worry you will easily reach a level that will worn you out. try to keep the 1:30 / 500m as long as you can. But never sacrifice the quality of your stroke (as show on the video) for either pace or strength (you could heart yourself).