You don't want to leave the majority of the work to your arms and upper body. Our legs are much stronger (generally) than our arms. Here are a few exercises to help increase your leg power.
Basically any plyometric leg exercise will work.
Hand Release Push Ups
Plyometric Push Up
Now that you've got the strength, you need to work on your speed, and speed (or sprinting) endurance. The best way to do this is to actually practice sprinting, or excreting high levels of energy for extended periods of time. Here are a few of my favorite high intensity drills.
Tabata: This is a 4 minute interval, 20 seconds high intensity, and 10 seconds rest, repeated 8 times. You can do this with basically any exercise, be it running, riding a bike, squatting, push ups... Just remember the higher the intensity the better.
Circuit: There are several different ways that a circuit can be performed. My favorite is 30 seconds on and 3 second transition alternating between a resistance exercise (squats, push ups, planks...) and a high intensity cardio exercise (buprees, mountain climbers, tuck jumps...) Here is a great one for you.
Here is a more complete explanation of High Intensity Interval Training.
Remember to practice rowing at least a couple of times a week, and work in these other helpful exercises on the other days. Some days will naturally be easier than others, but don't get discouraged!