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Tachometer on a 50hp electro shift '72'

S

skipper47

Contributing Member
For the last two years I have been building my boat up from a basic hull, I am fitting my 72 50hp Johnson electro-shift
on the back and I need to be fitting gauges, starting with a tach and a volt meter.
From the workshop manual it appears the the grey wire from the yellow plug goes to the tach, and then to earth?
My question is will any tach do? Here in the UK Johnson gauges are as rare as hen's teeth, but a decent set of Datcon blue
boat gauges have come up, is there anything I need to avoid or should know?
 
Nowadays, alternator tachs are pretty universal, so that's what you need. They work by counting the pulses from the alternator (grey wire). Different motors have different number of pulses per revolution, so the tach usually has a switch on the back to set the # of pulses. I have no clue concerning your Datcon.

Your '72 50hp should be 6 pulses per revolution (12 pole). Very common.
 
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Thanks fdrgator, most helpful and the 6ppr is very useful. I mentioned Datcon not knowing if they were a popular make with boaters or not.
The reason I mentioned Datcon is that all the gauges on ebay seem to be Honda, Suzuki, Yamaha etc.., and I don't want other outboard
manufacturers on the console when running a Johnson 50, and Datcon were the only other ones.
 
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