Re: 1970 50hp Mercury charging sytem
Hello to this forum,
I have been restoring a 14' fiberform runabout, with a 1970 Mercury 500
thunderbolt.
And your question is?? Assuming you're having issues with the charging system as indicated in the thread title, but typically you're gonna want to expound on that in your posting!
Your 50 has a very simple charging system: a stator under the flywheel, energized by magnets on the inner dia of the flywheel.
(2) wires come out to a rectifier which converts the AC signal to pulsating DC. There is no regulator, output is limited by the capacity of the stator windings (around 9-10 amps), and terminal voltage of your battery will vary depending on the type of battery and what electrical stuff you have turned on.
If it's not charging, likely the rectifier is at fault. In fact, probably 99 percent of the time it's the rectifier. The stator windings are easily checked with a meter; if you have a very low value of resistance (something on the order of 1 ohm or so) between the (2) yellow stator wires, the stator's good.
You can also check the rectifier with a meter to see if it's bad. Use the "Search" feature to find this info. "Rectifier Test" or similar oughta do 'er.
The later-style rectifiers aren't too expensive and if you have to refit one of these your only challenge will be finding a suitable place to mount it.
Search this site for any parts you need, if you have no luck try
www.mercruiserparts.com for diagrams/part numbers.
Last thought, never undo the battery cables while the motor's running. Never reverse battery cable polarity on the battery. The latter will pop a rectifier instantly, the former does them no good.
Well, hopefully that covers your questions, if not give another post and we'll take a stab at it..........ed
