OMC Faria Tach Swap

zigbat

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Jul 14, 2016
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1988 OMC 2.3L Cobra with motorola alternator

My original tach was Faria 6000 rpm tach that got signal from the coil
I bought a 7000 rpm tach not knowing it was to connect to the alternator of outboards only
It has a switch on ti to dial it to how many poles the alternator has 4,6,8,10,12
I believe my motorola alternator is 12 pole.. so if i run a wire to the signal input will it work
or are there other reasons that it wont besides the signal..
 

GA_Boater

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It won't work for an alternator, Zig. The number of poles are for a stator and the tach signal is AC voltage. If it works, the pulses are all wrong the the tach reading will be off.

There tachs that work with both 4 stroke and outboards as this one does, but only for 12 pole outboards and 4, 6 or 8 cylinder 4 strokes with the signal from the coil like your old tach.

tachset.PNG
 

sam am I

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Jun 26, 2013
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.........4 pole stator gives 2 pulses/rev

.........4 cylinder 4 stoke 2.3L gives 2 pulses/rev

Set your new tach dial to "4 poles" and hook it to the coil where the old tach was hooked (coil -)...........
 
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zigbat

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.........4 pole stator gives 2 pulses/rev

.........4 cylinder 4 stoke 2.3L gives 2 pulses/rev

Set your new tach dial to "4 poles" and hook it to the coil where the old tach was hooked (coil -)...........
 

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zigbat

Seaman
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Jul 14, 2016
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This is actually the second Faria tach I boight..
The first one was a 6000 rpm that looked just
like my old one but when I set it to the 1 position
it read about 800 lower than actual rpm which i
got by hooking a timing light to a spark plug wire
 

sam am I

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which i
got by hooking a timing light to a spark plug wire

I'm not clear about/why the timing light and the spark plug wire.........

As above and as your tach's instructions says, set to position #1 - 4 poles/cyls (2 P/R), then connect the tach's sig. wire to the "coil -" terminal which gives the same 2 P/R on your 4 stroke 4 cylinder motor. Apples to apples........
 

zigbat

Seaman
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Jul 14, 2016
Messages
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I used a timing light to get an accurate RPM to use against the RPM of the tachs for comparison,
my original tach was sticky and the second one was used and read about 800 lower than the timing light reading
I had the timing light (with built in tach function) hooked up while i ran the boat.. It was the only thing I had
that I could use that I figured was fairly accurate...

I understood ya, got it on 1 and about to go hook it up to the original harness now which will put it to the coil-

I just thought maybe there was an internal diffrence between tachs that hooked to alternators and ones to coils
but apples to apples...

Thanks
 

zigbat

Seaman
Joined
Jul 14, 2016
Messages
62
.........4 pole stator gives 2 pulses/rev

.........4 cylinder 4 stoke 2.3L gives 2 pulses/rev

Set your new tach dial to "4 poles" and hook it to the coil where the old tach was hooked (coil -)...........

worked like a charm...
Put it in the other day but didnt start it up till today..
havent really tested it but idle was real close and it sounded close at 1500
but its close enough to use the fine tuning to put it spot on...

Thanks.. I would have been stringing wire to the altenator probobly...
 
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