functions.php

<?php
/**
 * Grid Content
 * Change the number of words in excerpt if in the grid loop
 */
function be_grid_content() {
 
  // First, we make sure we're in the grid loop.
	if( ! apply_filters( 'is_genesis_grid_loop', false ) )
		return;
 
	// Only display excerpt if not a teaser
	if( !in_array( 'teaser', get_post_class() ) )
	  echo '<p>' . wp_trim_words( get_the_excerpt(), $length ) . '</p>';

	// Remove default content so we don't get both
	remove_action( 'genesis_post_content', 'genesis_do_post_content' ); // For Genesis 1.x
	remove_action( 'genesis_entry_content', 'genesis_do_post_content' ); // For Genesis 2.x
}
add_action( 'genesis_post_content', 'be_grid_content', 9 ); // For Genesis 1.x
add_action( 'genesis_entry_content', 'be_grid_content', 9 ); // For Genesis 2.x