120 Amp alternator replacement
I have a P42 with a Yanmar 4JH2TE (62 HP turbocharged diesel). It was originally sold in 1991 with an 80 amp OEM alternator. I replaced that alternator with a Lestek higher output alternator rated at 135 Amps cold and 105 amps hot. I have it hooked up to a 12 step voltage regulator made by Ample Power Company. (The 12 step regulator is just a fancier version of any 3 step high performance voltage regulator). It bolted into place with virtually no modifications to the engine or alternator. I have been using it for approximately 3,000 engine hours and it works great. I usually charge at anchor at about 1500 RPM, which gives me 65 amps after the alternator heats up (in about 10 minutes). I would have liked to have even a larger output alternator, or a second one installed as well. However, an experienced Yanmar service technician told me that would place an unacceptable load on the crankshaft pulley bearing. However, he thought my current set-up was fine. (And it has worked for a number of years of cruising and power generation). I purchased the Lestek alternator through Ample Power Company in Seattle, and I imagine it is similar to many others made by Balmar and other companies. It has dual hot bolts so that you can charge two battery banks simulataneously. However, since I use only a single house battery bank of (3) 8G8D batteries, I wired the two outlet bolts together.
