For cramping, try downing a banana before jumping in the boat. Sounds simple, but it works. For general soreness, if you're working out that much, make sure you're eating enough. Twice a day everyday is a lot of working out. Add to that a generally healthy lifestyle and you need a ton of fuel to support it.
Aside from that, consider your overall muscle balance. Your main muscles may be strong, but what about support muscles? If you use a lot of machines, try switching to a predominantly free-weight program and make sure you're hitting every muscle group each week. Free weights force the support/stabilizer muscles into action, and when you shore those up, you'll make big strength gains in your main muscles too.
P.S. I'm not a personal trainer, just a former fat guy who dropped 80+ lbs all on his own and now maintains 10% body fat and works hard to keep it that way.
And honestly, after a few years of going it alone with some books and magazines, I ended up trying that P90X infomercial DVD workout at the dare of a friend...it's all setup for you, changes every 30 days to keep muscles guessing and working, and it just plain works. Free weights, bodyweight, plyometrics, abs/core, even some yoga and stretching workouts. Everything is in there, and organized well.