No, the time dilation between Earth and Mercury is not significant enough to cause such a drastic difference in time. The effect of time dilation becomes more noticeable as objects approach speeds close to the speed of light, and the gravitational field they are in is extremely strong.
Mercury orbits the Sun at a relatively high speed, and it is also closer to the Sun compared to Earth. These factors do cause a small amount of time dilation, but the difference is not large enough to make 100 years on Earth equivalent to 500 years on Mercury.
In reality, the time dilation between Earth and Mercury is quite minimal. According to calculations based on the theory of relativity, if an observer on Mercury were to experience time for 100 years, an observer on Earth would measure a slightly shorter duration of time. However, this difference is only on the order of milliseconds or less over such a period.
So, while time dilation is a real phenomenon, it does not result in such dramatic differences in the passage of time between Earth and Mercury as you described.