Vintage Tachometer HELP

Joined
Dec 6, 2018
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6
I work at a dry stack boat marina and I just got an old Aqua Meter tachometer that was laying behind a shelf. I’m trying to figure out how to wire into my little project boat (1985 17ft Alindale well/net boat). The boat has a 2003 or 2001 Tohatsu 25hp 2 stroke (M25C3). I can’t seem to find a signal wire, but I have seen tach’s with the signal wire wrapped around the spark plug wire. The tach has four wires. It states what two of the wires go to (ground and pulse source) but I can’t seem to figure out what the other two black wire meant for. I’m sure at least one is for a power source. If anyone has any idea about it or even a small lead I can go on, please let me know
 

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Alumarine

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Feb 22, 2005
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Aren't the other 2 black wires for the light?
I'm thinking that might be a 4 stroke tach, most 2 stroke tach's I've seen go higher than 6K.
 
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Dec 6, 2018
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That's what I what I guessing that those two black wires are for the backlight. I was unable to determine which of the wires are positive or negative, but I could plug and check. I was able to find the proper wires for the hooking a tach to the motor, unfortunately those were two wires and this tach only requires the one. I'm going to do a little plug and play and see if I can get a response on the tach.
 

Mohawkmtrs

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Jan 13, 2010
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Marc...you're right about the light wires.

Operating RPM range (WOT) according to the manual: 5000-6000 RPM.

Russell: For a wiring diagram, google Tohatsu Outboard Manuals.

Set pulses per rev at 4.
 

tallcanadian

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Sep 7, 2006
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I sure do. He pm’d me already. I’ll get the instructions tomorrow. How’s things?
 

GA_Boater

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Thought maybe you could lend a hand and you were on it already. :thumb:

Thanks, TC.
 

tallcanadian

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So I have the info need for your tach. What is the process to get pics on here. I haven’t posted in forever and not sure how. Is there still a size limit?
 
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Dec 6, 2018
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Thanks for the help everyone. Marc c, the tach should work fine for my motor like, Mohawkmtrs said, the motor at wide open is 5000 - 6000 and I did find the owners manual with the wiring diagram in it. It say's to use the white and yellow wires for the tach, since this isn't a Tohatsu tach I know it's not going to be quite that simple. I can stick the ground wire from the tach into the black wire from the motor and I can stick the pulse wire from the tach into the white or yellow wires and both will make the tach respond. I'm not sure which one I should use, the yellow or the white wire? The black wire was just capped, but the yellow and white wire went into that rectifier that I posted a picture of. I'm also not sure what the purpose of those wires going into the rectifier are? The starter crapped out on me, so I've been using the pull start to test the tach. I'm a little worried with those wires not being plugged into the rectifier, the motor's electrical start will no longer work. This is the first motor I've ever really worked on and it was sitting for a long time for I got my hands on it. I was able to get it running pretty well and converted it from tiller to center console. I am still pretty green to this stuff and I've just been learning things as I go.
 

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Dec 6, 2018
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After a quick Google search I see that the rectifier is a component for charging the battery as the motor is running. I wonder if I could sacrifice the yellow or white wire for the tach and the rectifier still work fine without one of those wires connected. An update on the two black wire (backlight wires). I'm thinking that the backlight is shot, because I tried hooking it up to the boat's battery and the tach wasn't lighting up at all.
 
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GA_Boater

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I wonder if I could sacrifice the yellow or white wire for the tach and the rectifier still work fine without one of those wires connected.

The next thing we'll hear from you is the battery isn't charging. :smile:

Both the the white and yellow wires must be connected to the rectifier. What you do is tap into either one, white or yellow, and connect to the signal or pulse source wire on the tach.

tallcanadian Look at the Forum Help link in my sig and look at the picture attaching tutorial. There still is a size restriction. After you try to attach a pic, it will come back to you. We're here if it doesn't. :D
 
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