The maximum number of binary trees possible with \( n \) nodes is given by the \( n \)-th Catalan number. For 4 nodes, the Catalan number \( C_4 \) is:
\[
C_4 = \frac{1}{5} \times \left( \binom{8}{4} \right) = 14.
\]
Thus, the maximum number of binary trees with 4 nodes is \( 14 \).