These pulley kits by Balmar offer the opportunity to install a larger alternator than would otherwise be possible. this kit is for the Yanmar 3JH3. The kit include a set of serpentine pulleys for the crankshaft, water pump pulley and alternator. This pulley kit comes with two belts so you have a spare, the alternators need to be purchased separately. If you order an alternator at the same time as the kit it will come with the appropriate pulley pre-installed.