Tohatsu Tach

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dabren
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Tohatsu Tach

Postby dabren » Wed Aug 31, 2011 4:55 pm

Hello,

Does anyone know what colour wire on I tap into on a 91 Tohatsu for a tach sensor? Available ones I have are yellow (which is what I think it is from the little info I've been able to find online), white, and brown. They are all fastened with butt connectors in the harness in the engine. Here is a pic:

http://www.flickr.com/photos/36221784@N ... otostream/

If it is the yellow, when I separate the butt connector which one would I tap into, the male or the female (or top half/bottom half)?

I have the manual, but to be honest I can't tell if it's giving me the answer. It looks like going into the harness they label both the yellow and white 'rectifier lead wire' and on the way out they label both of them 'magnet lead wire'.

Any help would be great.
Thanks a lot,

Dan

Trackhappy
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Re: Tohatsu Tach

Postby Trackhappy » Wed Aug 31, 2011 6:15 pm

I assume 91 is the year, what model/size? Is the Tacho an aftermarket or one that comes with the engine?
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Trackhappy
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Re: Tohatsu Tach

Postby Trackhappy » Wed Aug 31, 2011 6:41 pm

What I can find so far is that a true Tohatsu tach has two wires that feed from the engine. These would be across the windings on the alternator to give the AC feed for the tacho. They have a 4, 6, and 12 pole switch on the back which also makes sense depending on model (number of magnets in the alternator). This means you connect the appropriate tacho to both yellow and white respectively, and it also has a battery or ignition feed and -ve at a guess. I found one diagram where the harness goes to the control unit then from there the wires come out to the gauges, but not sure if that is close to your model or not.

I suspect you may be trying to fit a standard auto tach, which may or may not work correctly. They have only a single feed normally off the coil wire plus ignition feed and ground.
By the time I have built a boat, I'll be ready to build a boat....

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dabren
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Re: Tohatsu Tach

Postby dabren » Wed Aug 31, 2011 6:46 pm

Yes sorry the engine is a 30hp, model M30A3 EP. Tach is a faria gauge. Instructions state to wire + to the ignition, and then wire the ground, and then the tach to SIG. The gauge does have the adjustment for the number of poles and I was able to track down the info and adjust for 4...

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dabren
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Re: Tohatsu Tach

Postby dabren » Wed Aug 31, 2011 6:47 pm

Maybe this won't work and I need to get a genuine Tohatsu gauge? The faria looks so much nicer though...

Trackhappy
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Re: Tohatsu Tach

Postby Trackhappy » Wed Aug 31, 2011 7:19 pm

Ok, it should work just hook the tach /SIG wire to either the yellow or white (doesn't matter which). It should get enough of a pulse off there to trigger. Assuming it does, then you just need to verify that it is reading correctly somehow.
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gdcarpenter
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Re: Tohatsu Tach

Postby gdcarpenter » Wed Aug 31, 2011 7:20 pm

Don't know if this helps - but if you can deduct or trace which wire is on the stator output circuit that is the one that should go to the 'signal' terminal of the tach. The stator puts out an 'alternating' signal and the tach should be set to the number of magnets in the stator.
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Trackhappy
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Re: Tohatsu Tach

Postby Trackhappy » Wed Aug 31, 2011 7:33 pm

One other comment, depending on the rectifier it may work on one but not the other (yellow or white). If it has a full wave bridge rectifier it will work on either, but a half wave or single diode will have one side too low to detect. Smaller/cheaper engines somethimes just have a single diode in there and no regulation at all. Not sure about yours.

GD is spot on by the way, the yellow and white are the wires from the stator.

Edit:

Manual is here: http://www.tohatsu.com/tech_info/own_ma ... 2_30A3.pdf

Last pages have diagrams and confirm rectifier is full wave bridge so either wire will be fine for SIG.
By the time I have built a boat, I'll be ready to build a boat....

DuckyNut
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Re: Tohatsu Tach

Postby DuckyNut » Wed Apr 10, 2013 12:24 am

Hi Dan

Just found this thread via Google search
I find that I am in the same boat as you were in - pardon the pun :roll:

Have just bought a new Tohatsu M30H EPS to put on my Rubber Ducky project - a long story
That's a 30hp remote control engine for those who don't know the Tohatsu coding ( I didn't until I got it )
The electrical diagram in the Owner's Handbook shows the Tohatsu tacho with the 2 wire hook up as you described
I want to use the Teleflex Amiga series instruments and the tacho only has a single signal wire
similar to what you were doing with your boat

So question is - how did it go - successful tacho install :?:
If so, would appreciate advice on what wire you connected the tacho signal wire to

Hope you can help

Chris


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