Help wiring Tach

[Johnny HotFoot]

I have a Teleflex Tach on the way for my 1978 Merc OB, 900, 90HP

I can wire the + and ground without much ado, but I am a bit frazzled with the task of wiring the signal wire.... where on the motor do I go with it, and more importantly, how the heck do I go about feeding the wire through the transom and out to the motor???

Do I just wrap the wire around the outside of all the other lines that go to the motor and are neatly ran inside a black cover???

The simpler the install the better.... in another year or two I will be re-doing the entire boat and can un-fudge the mess I make this week...http://checkmate-boats.com/forums/images/smilies/biggrin.gif

Thanks...

[ProComp]

Typically there is a Tach wire in the main harness that comes up to the front of the boat. On the newer Mercs I believe its the Grey wire. Not sure about your year. Maybe take a quick look.

[Johnny HotFoot]

I doubt I'll get lucky and find a tach lead inside the control box....so assume I'll be taking the wire all the way to the engine itself....where do I tap in?

[Diablo Dan]

Look near the rectifier/ regulator for a tach lead- should be grey.

Reg/rect also has yellow ( from stator), red, black and grey wires.
Tach signal is generated by the charging system.

Dan

[ZonkaRacing]

WHen you buy the gauges dont they come with a diagram that says were everythings supposed to be wired?

[The Big Al]

On the older units! (like you have)
You need a tach harness that plugs into the Shifter control box.
You can get this harness from your local dealer or bass-pro shops.
Click on this link
http://www.basspro.com/webapp/wcs/stores/servlet/SceneSevenDisplay?catalogId=10001&storeId=10151&langId=-1&section=Home&productId=-33233&scene7Path=BassPro%2f531-212-00%3flayer%3dcomp%26wid%3d500%26hei%3d500%26fmt%3djpeg%26qlt%3d100%2c0%26op_sharpen%3d0%26resMode%3d trilin%26op_usm%3d1.0%2c1.0%2c0.0%2c0%26iccEmbed%3d0&sourceName=images2%2f500-000%2f531-212-00.jpg&type=0&linkEnabled=false

<TABLE><TBODY><TR><TD></TD></TR></TBODY></TABLE>http://img528.imageshack.us/img528/9848/mercurytachharenesstg0.jpg (http://imageshack.us)
Shot at 2007-08-09<!-- End - JSP File Name: SceneSevenBody.jsp --><!-- BEGIN LayoutContainerBottom.jspf --><!-- /Content --><!-- Start - JSPF File Name: JSTLEnvironmentSetup.jspf --><!--c:out value="include/styles/style1/"/--><!-- End - JSPF File Name: JSTLEnvironmentSetup.jspf --><!-- BEGIN ContentContainerBottom.jsp --><!-- This file is empty. Add content here that you want as a common wrapper for your main content. --><!-- End - JSP File Name: SceneSevenBody.jsp --><!-- BEGIN LayoutContainerBottom.jspf --><!-- /Content --><!-- Start - JSPF File Name: JSTLEnvironmentSetup.jspf --><!--c:out value="include/styles/style1/"/--><!-- End - JSPF File Name: JSTLEnvironmentSetup.jspf --><!-- BEGIN ContentContainerBottom.jsp --><!-- This file is empty. Add content here that you want as a common wrapper for your main content. -->

[The Big Al]

<TABLE cellSpacing=0 cellPadding=2 bgColor=#ffffff border=0><TBODY><TR><TD class=item align=middle bgColor=#c6cdcf border="1">Order
Qty

</TD><TD class=item align=middle border="1">Your
Cost

</TD><TD class=item align=middle>Item
Number

</TD><TD class=item align=middle>Description</TD><TD class=item align=middle>Size</TD><TD class=nothing align=middle></TD></TR><TR style="BORDER-LEFT-COLOR: #0000ff; BORDER-BOTTOM-COLOR: #0000ff; BORDER-TOP-COLOR: #0000ff; BORDER-RIGHT-COLOR: #0000ff"><TD class=item align=middle bgColor=#c6cdcf border="1"><LABEL for=WC_CachedProductItemDisplay_FormInput_quantity_In_OrderItemAddForm_1_1></LABEL><INPUT id=WC_CachedProductItemDisplay_FormInput_quantity_In_OrderItemAddForm_1_1 maxLength=2 size=2 value=0 name=quantity_-269087 cM1="1" cM3 cM2="9"> <INPUT type=hidden value=-269087 name=catEntryId_-269087 cM1="1" cM3 cM2="10"> </TD><TD class=item noWrap align=right><!-- Start - JSP File Name: CatalogEntryPriceDisplay.jspf --><CENTER>$24.99 </CENTER><!-- End - JSP File Name: CatalogEntryPriceDisplay.jspf --></TD><TD class=item noWrap align=left>38-531-212-00 <INPUT type=hidden value=38-531-212-00 name=in_-269087 cM1="1" cM3 cM2="11"> </TD><TD class=item align=middle>TACH HARNESS</TD><TD class=item align=middle>MERCURY</TD></TR></TBODY></TABLE>
Bass pro Shops part number

[Johnny HotFoot]

<TABLE cellSpacing=0 cellPadding=2 bgColor=#ffffff border=0><TBODY><TR><TD class=item align=middle bgColor=#c6cdcf border="1">Order
Qty


</TD><TD class=item align=middle border="1">Your
Cost


</TD><TD class=item align=middle>Item
Number


</TD><TD class=item align=middle>Description</TD><TD class=item align=middle>Size</TD><TD class=nothing align=middle></TD></TR><TR style="BORDER-LEFT-COLOR: #0000ff; BORDER-BOTTOM-COLOR: #0000ff; BORDER-TOP-COLOR: #0000ff; BORDER-RIGHT-COLOR: #0000ff"><TD class=item align=middle bgColor=#c6cdcf border="1"><LABEL for=WC_CachedProductItemDisplay_FormInput_quantity_In_OrderItemAddForm_1_1></LABEL><INPUT id=WC_CachedProductItemDisplay_FormInput_quantity_In_OrderItemAddForm_1_1 maxLength=2 size=2 value=0 name=quantity_-269087 cM2="9" cM3 cM1="1"> <INPUT type=hidden value=-269087 name=catEntryId_-269087 cM2="10" cM3 cM1="1"> </TD><TD class=item noWrap align=right><!-- Start - JSP File Name: CatalogEntryPriceDisplay.jspf --><CENTER>$24.99 </CENTER><!-- End - JSP File Name: CatalogEntryPriceDisplay.jspf --></TD><TD class=item noWrap align=left>38-531-212-00 <INPUT type=hidden value=38-531-212-00 name=in_-269087 cM2="11" cM3 cM1="1"> </TD><TD class=item align=middle>TACH HARNESS</TD><TD class=item align=middle>MERCURY</TD></TR></TBODY></TABLE>
Bass pro Shops part number


Thanks.... forums are only great if the people are!!!

[Johnny HotFoot]

On the older units! (like you have)
You need a tach harness that plugs into the Shifter control box.
You can get this harness from your local dealer or bass-pro shops.
Click on this link
http://www.basspro.com/webapp/wcs/stores/servlet/SceneSevenDisplay?catalogId=10001&storeId=10151&langId=-1&section=Home&productId=-33233&scene7Path=BassPro%2f531-212-00%3flayer%3dcomp%26wid%3d500%26hei%3d500%26fmt%3djpeg%26qlt%3d100%2c0%26op_sharpen%3d0%26resMode%3d trilin%26op_usm%3d1.0%2c1.0%2c0.0%2c0%26iccEmbed%3d0&sourceName=images2%2f500-000%2f531-212-00.jpg&type=0&linkEnabled=false

<TABLE><TBODY><TR><TD></TD></TR></TBODY></TABLE>http://img528.imageshack.us/img528/9848/mercurytachharenesstg0.jpg (http://imageshack.us)
Shot at 2007-08-09<!-- End - JSP File Name: SceneSevenBody.jsp --><!-- BEGIN LayoutContainerBottom.jspf --><!-- /Content --><!-- Start - JSPF File Name: JSTLEnvironmentSetup.jspf --><!--c:out value="include/styles/style1/"/--><!-- End - JSPF File Name: JSTLEnvironmentSetup.jspf --><!-- BEGIN ContentContainerBottom.jsp --><!-- This file is empty. Add content here that you want as a common wrapper for your main content. --><!-- End - JSP File Name: SceneSevenBody.jsp --><!-- BEGIN LayoutContainerBottom.jspf --><!-- /Content --><!-- Start - JSPF File Name: JSTLEnvironmentSetup.jspf --><!--c:out value="include/styles/style1/"/--><!-- End - JSPF File Name: JSTLEnvironmentSetup.jspf --><!-- BEGIN ContentContainerBottom.jsp --><!-- This file is empty. Add content here that you want as a common wrapper for your main content. -->


OK, I got the wire harness and for a second i thought I was going to be on easy street with the install, but on the front of my Mercontrol Box the round black rubber 'plug' has 3 flat female terminals (2 side by side and a third perpendicular) and the bottom one has a yellow wire fed into it..... the harness has 5 female wholes (small circles that will accept small round 'pins')..... now what???

[Diablo Dan]

There are three or four different harnesses.
3, 4 or 5 pin.

The three pin is listed in the Mercury parts catalog as I was searching for one on Thursday for a job at work.

I'll check the numbers today ( Saturday) when I get to the shop.

Dan

Alrighty then,

The 3 blade style adapter is part # 84-46239A1 MSRP: $30.62
They are in 3 warehouses ( Fond du Lac, NJ, CA).

I have a similar harness from a tilt/trim that you can have for the asking.
Wiring colors are different, but should not be difficult to make it work.
I can post pics tonight as Photobucket is blocked at work.

Dan

[Johnny HotFoot]

There are three or four different harnesses.
3, 4 or 5 pin.

The three pin is listed in the Mercury parts catalog as I was searching for one on Thursday for a job at work.

I'll check the numbers today ( Saturday) when I get to the shop.

Dan

Alrighty then,

The 3 blade style adapter is part # 84-46239A1 MSRP: $30.62
They are in 3 warehouses ( Fond du Lac, NJ, CA).

I have a similar harness from a tilt/trim that you can have for the asking.
Wiring colors are different, but should not be difficult to make it work.
I can post pics tonight as Photobucket is blocked at work.

Dan


OK, so I should return the 5-pin and look for a 3-blade harness, which will plug right in to my ancient Mercontrol and feed a tach signal to my guage????

If you have the right 3-blade harness, I'm sure I could make it work with my guage, let me send you a little something and/or at least cover the shipping if you have one for me...

[Diablo Dan]

http://i44.photobucket.com/albums/f3/Target13/TachHarness001.jpg

Pic here.
I think that it will work. just a matter of decoding the wire colors.

Let me know.
Going to the lake for the weekend. Back on Monday.

Dan

[Johnny HotFoot]

OK.... I almost out of the woods on this tach install.... now who can help me with decoding the 3 female terminals on the front of my older Mercontrol.... there is a single female slot at the bottom, flat to the ground, and then there are 2 side by side female slots running up and down like a plug in the wall at home.... as of right now there is a yellow wire shoved into the bottom ,flat slot... I haven't traced it yet to see where it leads, but I do need to know what these three female terminals are representing.... any help? Thanks in advance....

[Johnny HotFoot]

OK.... I almost out of the woods on this tach install.... now who can help me with decoding the 3 female terminals on the front of my older Mercontrol.... there is a single female slot at the bottom, flat to the ground, and then there are 2 side by side female slots running up and down like a plug in the wall at home.... as of right now there is a yellow wire shoved into the bottom ,flat slot... I haven't traced it yet to see where it leads, but I do need to know what these three female terminals are representing.... any help? Thanks in advance....

To be crystal clear I'm asking for help identifying theses three 'outputs':
bottom single and flat slot, top inboard slot, top outboard slot

[The Big Al]

Johnny what year is this thing?

[Johnny HotFoot]

Johnny what year is this thing?


The plate on the motor reads 1978, if I'm not mistaken... the "8" looks smudged, like it may have been a 6 or something and altered to look like an 8, but who would do that?

[Johnny HotFoot]

OK.... I almost out of the woods on this tach install.... now who can help me with decoding the 3 female terminals on the front of my older Mercontrol.... there is a single female slot at the bottom, flat to the ground, and then there are 2 side by side female slots running up and down like a plug in the wall at home.... as of right now there is a yellow wire shoved into the bottom ,flat slot... I haven't traced it yet to see where it leads, but I do need to know what these three female terminals are representing.... any help? Thanks in advance....


To be crystal clear I'm asking for help identifying theses three 'outputs':
bottom single and flat slot, top inboard slot, top outboard slot

[Johnny HotFoot]

Bump-titty-bumb-bump

[Johnny HotFoot]

Here's a thought.... can I hook up my new teleflex Tach to my old 3 blade plug Mercontrol and it will work, or do I have to move a wire under the cowling to get a new tach to work with an old Merc OB (1978)????

[Johnny HotFoot]

bump.... gonna try to start the install this week and need more info...

[Johnny HotFoot]

bump.... gonna try to start the install this week and need more info...


.......:(

[Johnny HotFoot]

no one can help me?

[Diablo Dan]

What color wires are at the connector?

Purple = 12v w/ key on
Grey = tach signal
black= ground

Someone may have used the yellow wire for 12v

If the wires are blue & green, they are for tilt & trim.

[Techno]

It should be a tach connection if its on the front of the box.
This connector style is used for trim but only at the back for the trim unit, not on the control box, and not on the front going to the dash.
Neither uses yellow.

The old book I have is showing it to be tach. black brown white.
Yellow is showing as your neutral safety switch, it shouldn't go to this connector. If the internal snap switch is shot maybe this is how they bypassed it. All you need to do though is bypass the switch and not lead it to the tach plug on the front of the box.
Gray is also showing as your choke enricher, not your tach.
The colors for the tach shouldn't matter since they are set to go where they spoda go.:D The top, r-side, l-side.

I suggest going to one of the car stores in your area and pick up an old manual. I think thats where I got mine.

The round pin plugs are for boat harness to engine harness.
This all gets confusing if you don't have the schematic to see it all drawn out. Since you have a yellow wire where it shouldn't be I would get the book.
It looks like the color code is being changed in this era.

[sho305]

My old book shows the flat three blade plug as a trim control plug. The dash/tach plug has round pins and is towards the bow, opposite of the large harness to the motor. They have pins on one side of a round connector in an arc.

The tach wire will be brown or gray depending on year, my book is not very clear. It will go to the recifier to one of the wires from the stator. Rectifier has two from under flywheel that make AC...it goes to one of those. The third wire on rectifier is Red 12v+ (DC) you get power/charging from.

I'm not 100% sure because I don't know exactly what motor you have, this book has a pile of diagrams you have to match them up with your boat more or less. It SHOULD have a wire in the harness if you have the big factory harness up to the front to controls/key. I would look at wires, find one taped off that is gray or brown...look at your motor for the rectifier and see what is on it. Usually about a 1" square thing near flywheel bolted to something that heat sinks it like a starter bracket or something. The red wire from it will go to hot on solenoid/etc. My '73 and '76 inlines had plug right on front of control box, wires ran up to dash...they use the other ones usually not always.

I just put one on my chrysler and had no hot on the key, I had to use the overheat alarm wire to power the tach. That is the + power wire, not the signal wire we are talking about above. Signal is from the alternator that charges under flywheel, it often has other wires and separate coils in there for ignition or pickups...they will go to switchbox or coils/etc. A few smaller motors in the book have a big switchbox on the motor and tach goes to that but way you describe I think its not that one.

For example here is a 5 wire harness like you bought:
Purple---12+
Black---Ground
Gray---Tach signal
Brown/white---Trim indicator gauge signal
Tan---Alarm horn (overheat I would guess)

Older ones have less wires, often the first three and some tach is brown.

That would be never than my '73 as it has no overheat sensor. The tach/trim gauges and alarm horn are completely run with those wires.

Like I said, if you don't have the plug but have the big factory harness, those wires should be in the harness and same color all the way to motor. Tell me what colors are on your rectifier.