[spareparts]

no need to add more zinc, just make sure the zincs you have are properly grounded, use an ohm meter and check for continuity between all parts of the drive to a sutable gound inside the boat. clean the surfaces behind the mounting locations for the zincs, use the supplied star washers to improve contact( especially the one that comes with the new prop that everyone throws away), keep the zincs fresh by scrubbing them with a wire brush. If you keep your boat in an area thats doesn't have a lot of current( tide current not electrical), you might consider a Mercathode system( electronically replaces teh zincs) but you will need shore power of some sort to keep the battery from going dead. Soem people add zincs to the trim rams on older drives, check for interference. The easiest thing to do is to add a zinc grouper, its a big zinc( shaped like a fish for appearance only), that has a gounding cable and a lanyard to cleat it off, just clamp the cable to the engine block or sutable ground and tie the lanyard to a cleat and drop it iin the water. Don't forget to pull it out before using the boat!. If you really want to get into it, Mercruiser has a worksheet that walks you thru all the corrosion test, you're required to fill it out before submiting a corrosion claim uunder warranty, it takes a while to do it, but it will find a problem. You might want to take a look at the boats around your slip, don't keep your boat near older junkers if your using shore power, their electrolisys problem can become your problem thru the ground wire of shore power if you dont have an galvanic isolater