Append a text string to WooCommerce single product title

remove_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_title', 5 );

function woocommerce_template_single_title_custom(){
    $additional_text = ' More Info';
    the_title( '<h3 class="product_title entry-title">', $additional_text.'</h3>' );
}
add_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_title_custom', 5);