This service repair workshop manual covers the Yanmar HA Series and HAL Series diesel engines, specifically the industrial models 4HAL and 6HAL, and the marine models 6HAE, 6HA-HTE, and 6HA-DTE. Engineered for reliability and performance in demanding marine and industrial applications, these engines are built to the high standards expected from Yanmar. This manual provides comprehensive information to ensure optimal operation and longevity of your engine. The purpose of this manual is to serve as a complete guide for the maintenance, repair, and troubleshooting of your Yanmar HA Series/HAL Series engine. It includes detailed, step-by-step instructions, hundreds of photos and illustrations, and covers a wide range of topics from general information and routine maintenance to in-depth procedures for the cylinder head, engine proper, lubrication, cooling, fuel, intake, exhaust, and electrical systems, as well as the marine gear and engine installation. This resource is designed to assist both DIY enthusiasts and experienced mechanics in keeping their engines in peak condition.