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Old 21 January 2012, 14:14   #1
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rev tacho help

i have a 30hp yam 2 stroke 2002 , i tried to add a yam rev counter 6 pole analog today and nothing. i added a positive from battery to rev counter so batt to rev , ground to rev counter was negative from battery, send was green from outboard, started up outboard and ........nothing?

help
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Old 22 January 2012, 06:14   #2
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Multimeter time:

dc Voltage (20 V scale) between POS and Ground
ac voltage (20 V scale) between SIGNAL and Ground

Stupid question - is the battery connected to the engine?
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Old 22 January 2012, 08:00   #3
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i have a 30hp yam 2 stroke 2002 , i tried to add a yam rev counter 6 pole analog today and nothing. i added a positive from battery to rev counter so batt to rev , ground to rev counter was negative from battery, send was green from outboard, started up outboard and ........nothing?

help
did you connect the rev counter to the same boat that the engine is on?
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Old 22 January 2012, 11:09   #4
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thanks guys!

info..yam 30hp two stoke pull start man tilt therefore no battery.
second hand yamaha 6 pole un adjustable rev counter.

polwart 1st...........what i tried was adding a 12v battery into boat .

positive battery to rev counter positive
negative battery to rev counter ground
blue wire on outboard to rev counter send

started up nothing checked connections, checked battery fine

mister p........... yes
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Old 22 January 2012, 11:33   #5
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xs 400 - if I am reading that correctly you only have one wire connecting the engine to the gauge - ie. the battery is a standalone power supply not connected to the engine. I don't think that will work, the tacho is measuring pulses of voltage (probably not the right term). For their to be a voltage there must be two connections. Normally the ground (battery negative) is also connected to the engine ground and so provides the second connection.

If it were me I would attach engine ground to battery negative and see where I get to. However there may be some reason I've not thought about why that is a bad idea - so I'd hang on and see what other folks suggest.

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Old 22 January 2012, 12:40   #6
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I think you would need to connect positive, negative (ground) and exciter wire from the engine to the rev counter. If your Yam has an alternator then you might need a rectifier to ensure that you produce DC and not AC. As this would produce a pulsed current the rev counter may give misleading readings. This might be when a battery would need to be connected.
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Old 22 January 2012, 13:50   #7
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positive battery to rev counter positive
negative battery to rev counter ground
blue wire on outboard to rev counter send
Won't work. You've got no reference between the battery and the engine. Tie the battery (-) to a point on the engine block, and see what that does.



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Old 23 January 2012, 12:07   #8
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i have a 30hp yam
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Originally Posted by xs 400 View Post
blue wire on outboard to rev counter send
I may be wrong here, but I think Yams use a green wire for the Tacho signal.


If it's a pull start engine, does it even have an alternator to hook the tacho up to? - Outboard tachos count the pulses from the alternator, not the pulses to the spark plugs. It's unusual for a pull start engine to have a charger circuit, although some do for auxiliary lighting etc.


Follow your Blue wire back to the engine. it should end at a small black box with three terminals - one with a red wire (or nothing if you don't have a battery to charge), the other two yellow* wires dissappear up under the flywheel. Your "tacho signal" wire should share one of the yellow* wires' connections (the two halves of the AC out of the alternator), and the battery & engine will also need a common ground.

If you don't find something like that, tell us where the blue wire finishes. Post a pic or six if need be!


Edit:

* these two wires might be green - I am having a mental block between Yam & Merc... Either way, they dissapear under the flywheel!
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Old 23 January 2012, 13:06   #9
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I think your right, I beleive send is green, bit of a slip on my part i first said the send was green, then in a later thread Blue? sorry

as far as an alternator, it has a (2p) socket for lights on the front
and my hand book says alternator output 12v 80w?

is this ac?

the consensus seems to be i need

send ....rev counter send back to female green on outboard
earth....rev counter back to earth black on outboard.
battery....rev counter back to ?


question do I have to add a 12v battery to have a rev counter ( as man start and man tilt I dont have one, and would prefer not to .

can the battery go straight back to red positive on outboard?
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Old 23 January 2012, 14:09   #10
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Personally I'd look at adding a small battery to the boat and wiring it in so it is charged by the engine - then it can run vhf/sounder/chartplotter/gps or other gadgets you might want to add. It shouldn't be a major issue to add a regulator/rectifier if the lighting circuit is unregulated.

If you want to keep the battery separate then:

Signal - Green wire from engine
12V Pos - Battery positive
Ground - to both engine ground AND the battery negative

It may be possible to wire it direct to the red and black connections at the engine but it will depend whether the power output is properly rectified (dc) and regulated - otherwise you may just fry the tacho.
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