jmc

A point-slope form of the equation is $$y-(-3)=\frac{1}{2}(x-2).$$Multiplying both sides by 2 gives $2(y+3)=x-2$, and rearranging this gives $x-2y=8$. Letting $x=0$ and solving for $y$ gives us the desired $y$-coordinate of $\boxed{-4}$.