1983 Johnson 70-HP, Alternator Voltage Regulation, non-OEM replacement

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
mgajim
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1983 Johnson 70-HP, Alternator Voltage Regulation, non-OEM replacement

Postby mgajim » Tue May 17, 2016 3:54 pm

Gentleman--I have a 1983 Johnson 70-HP outboard engine [whose alternator] is putting out [a charging output of] upwards of 17-volts [when the engine is] running fast.

Do readers have experience with the CDI 193-3408 regulated rectifier?

I would like to try it, but I've had a bad experience not using factory parts.

jimh
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Re: 1983 Johnson 70-HP, Alternator Voltage Regulation, non-OEM replacement

Postby jimh » Tue May 17, 2016 4:00 pm

I suspect that the CDI part is an aftermarket part that improves the charging output by adding voltage regulation. If there is no equivalent OEM upgraded part, I don't see that there is much concern for getting an aftermarket part from CDI. CDI seems to be making a better-than-OEM part in many cases.

Rbrown
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Re: 1983 Johnson 70-HP, Alternator Voltage Regulation, non-OEM replacement

Postby Rbrown » Tue May 17, 2016 9:15 pm

On a 1989 Johnson 70-HP engine I owned, I replaced a defective rectifier with one from CDI, and it worked fine. But, if you are seeing high voltage on yours, you first may want to look into the condition of the battery and connections. Since this is an unregulated system, using only a rectifier, it requires a battery that is in top condition to maintain reasonable voltage levels. Otherwise, if the battery is not holding a proper charge, is the wrong capacity, or just old, the system will reach higher voltages in an attempt to recharge the battery.

Rbrown
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Re: 1983 Johnson 70-HP, Alternator Voltage Regulation, non-OEM replacement

Postby Rbrown » Tue May 17, 2016 9:27 pm

I do see that the rectifier you are thinking of buying now comes with a built-in regulator. That sounds like a good idea, but the standard rectifier system should work fine if everything else is up to par. Looks like that new rectifier is also about three-times the cost of a standard one.

jimh
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Re: 1983 Johnson 70-HP, Alternator Voltage Regulation, non-OEM replacement

Postby jimh » Thu May 19, 2016 9:40 am

Relying on the battery to act as a voltage regulator was an acceptable strategy for designing an outboard engine in 1940, but it makes no sense today. The added cost of buying a regulator as part of the replacement part is negligible. Unregulated charging outputs can cause many problems. See

http://www.cdielectronics.com/blog/regulated-rectifier/