Don has a 1957 Atom with reversed battery connections. I don't believe this is correct for a Greymarine 70. His grandfather who owned the Atom must have been a Ford man because Fords in the thirties used positive battery ground to the chassis. Or else someone inadvertantly reverse polarized the generator field coils and reverse installed the battery, and possibly the ammeter, to match.
If with the battery installed negative to engine frame, and the engine not running, the ammeter, unless it has reverse connections, should move in the discharge direction when lights, ignition, etc are turned on. If, however, the ammeter moves in the charge direction, the generator has probably been reverse polarized and the ammeter reverse connected. Either way works, but there are those who will argue that reverse current flow through the ignition points is not a good thing.
The iron cores of the generator field windings are magnetic and will have a small residual magnetism when the engine is shut down. This magnetism is enough to start the generator charging and quickly increases as the generator comes up to speed. If this small initial magnetism is backward, the generator output will be reversed.
To properly set up the field windings, current must be sent through them in the direction it will go when the generator begins charging. The procedure is described in Peterson's Basic Ignition and Electrical Systems Book #2. Any competent generator shop will do this at minor cost.
Because of the boat's history, I advise Don to buy a cleanup/checkout of the generator and cutout before proceding.
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Robert
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