I used to think that there wasn't much of a relationship between MCAT and SAT scores, but after reflecting on this further, I've come to the conclusion that there may be. When I first started studying, I told my friends that the MCAT was "different" from the SAT because it required "actual knowledge," blah blah blah. But after studying for it and taking it, I think that about 30-40% of the MCAT is knowledge while the rest of it is just test-taking ability. The test is unique in its format, and it's just silly a lot of regards. Just knowing your science won't get you a good score on the MCAT, unfortunately.
SAT: 1590
MCAT: 39R
I think that I did well on the SAT and MCAT because I was familiar with their formats and had established a test-taking "routine" by the time that I actually sat for them. Knowing science is good, but that's strangely not the most important requirement for a good MCAT score. *shrug*