I suggest you replace your Hitachi with the Balmar and keep the Hitachi as a spare. Dual pulleys and high side loads on the ENGINE bearings that result are not good for small diesels. You mitigate this somewhat with dual alternators as close to 180 degrees opposed as possible but there is NO need for a separate alternator for the starter only as VERY few amp hours are used in starting...high amps for a few seconds do not matter much and you can either get a dual output regulator (3 stage of course) or simply echo charge the starter battery. We did 4x8d's and a starter battery with a single 110A Balmar and it all worked out fine. You will have approx. 300ah's available for house amps and this means you will run your engine for 2-3 hours every 2-3 days to get back to 90% charge levels given a 100-150ah per day use.
Of course this is not good for your engine but many do it and alternatives are quite expensive. A lot depends on your cruising plans and how many years you plan to be out for.
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