Our marine Universal 5421 Serpentine Pulley Upgrade Kit is very easy to install. Allow approx. 2 hours and 20 minutes the first time you do this simple installation. When purchasing any Electromaax marine alternator the pulley in this kit can be installed for you at the factory. The new serpentine (micro ‘V’) crank pulley simply slips over your current crankshaft pulley and is secured with the bolts supplied. The new serpentine water pump pulley simply replaces your original. When replacing the original O.E.M. alternator with your new Electromaax high output marine alternator, be sure to read the wiring instructions prior to installing the unit. Helpful install hints 1. When loosening the 4 water pump bolts leave the existing belt in place THEN undo the bolts. This way you can use the belt to stop the W/P pulley spinning. 2. Check the threads in the existing crankshaft pulley have not rusted. We find in most cases a little grease on our bolts clean the threads out if you carefully put them in half a turn and back. Alternatively you can use the correct thread chase This popular Universal Marine 21 HP. engine, and all other engines operate much smoother, quieter and virtually eliminate belt dust with a serpentine pulley upgrade kit. Additional benefit of an Electromaax kit is the ability to drive auxiliary devices ie: Seafrost refrigeration, engine driven water maker, second alternator, compressor… with the addition of a second crankshaft pulley. Contact us for further details You can now safely operate the Electromaax FM-12-80, 100 or 120 amp marine alternators that produce up to 70% of their output at fast idle.