I bought this as replacement alternator for my Vovlo Penta 8.1 Gxi-a. The old Vovlo Penta alternator had rusted solid as it sat out under cover for the past year. You can imagine my surprise when I started the boat and immediately saw thick back smoke coming off the serpintine belt. This API marine had the best price and it arrived in about 10 days. Despite that it was advertised as a direct replacement the 2 mouting bolt hole very about 1/32" too small to fit the existing bolts. The bolts are threaded so using smaller bolts wouldn't work so I had to buy a 27/64 (closest I could find at the local hardware store) and drill out the holes. I braced the alternator between two 4x4's with the pulley down and then used an 18V cordless drill to overbore the holes. The drill bit cut easily and I had not problem acheiving a nice straight bore. Sending the alternator back and waiting another 2 weeks was not an option as I'm in the process of selling the boat. Once installed it seemed to work fine. I'm giving it 3 stars because of incorrect sized mounting holes and the need to drill them out. Note I did use the exact part number off of the original alternator and API Marine version was listed as direct replacement.