I went from a 35 amp to 85 amp and my batteries are much happier. I don't motor a lot and I was never really getting enough charge with the 35 amp alternator. I do notice more load on the engine so you may find you need to bump up the revs a bit to get the same cruising speed if your batteries are deeply discharged. It's small but noticeable. Make sure the wiring from your alternator to the batteries is large enough to handle the increased current. Your cables from battery to the engine are likely OK since they need to handle starter current but run through the entire charging circuit to make sure there aren't any week links. Oh, and clean all connections, I found some corrosion in mine when doing this.