OMC Tach ID?

[bralex]

I would like to find out if there is a reference for OMC tachs. What I'm looking at is a 1993 Lowe 1600 with a 40hp Evinrude. Not sure if the tach is working correctly. Would like to find ID info for a exact replacement with out removing the original. The removal will be a bit of a challenge with the console/deck design of the boat. Any guidance would be appreciated!

Thanks!

 

[Silvertip]

Re: OMC Tach ID?

Finding an exact original will be a challenge but chances are the tach was made by Faria or Teleflex. Any of their outboard tachs will work on that engine and will be a direct replacement. Four wires. 1) light, 2) +12V with switch on, 3) ground, and 4) sense. Set the calibration dial on the back to 6 pulse.

 

[bralex]

Re: OMC Tach ID?

Silvertip,

Thanks for the reply! I think that I found an original tach. It has the same face, size, etc but I can't see the id tag on the original. That's why I was hoping to find some sort of reference. I want to make sure the possible replacement is indeed the correct unit. I'm don't know how many different models may have had the same case and face?

 

[ezeke]

Re: OMC Tach ID?

Two dial tachometers (Tech Series) were listed for 1993 - they were part # 174887 - non plug-in and part # 174888- plug-in. Both were 7000 RPM and had setting for 5p or 6p.

Two digital tachometers (QUARTACH) were also listed - part # 174625-non plug-in and part # 174013 -plug-in.

The Tech Series tachs should not be hard to find since they are still on the market. I don't know about the digital.

 

[HighTrim]

Re: OMC Tach ID?

Before you go buying a new tach, I would test your current one first to ensure it is infact dead. Just because it is acting up, do not instantly blame the tach.

It is easiest to check for 12-volt power and proper ground first. A volt-ohmmeter or 12-volt test light are great tools for this procedure. Simply ground the meter or light, turn the key on and touch the positive probe to the purple wire on the back of the tach. You should see 12 volts indicated on the meter, or if you?re using a test light, its bulb should illuminate. Reverse the leads to check for proper ground, or use the ground wire on the tach to ground your meter or test light.

If either the power circuit or ground is the culprit, you can repair the problem and the tach should work fine. In a no-power situation, see if your tach has an inline fuse. These often blow due to constant vibration. After inspecting for power and ground, if it still doesn?t work, it?s time to check the signal-input source, or the tach itself.

A simple way to determine if the tach is bad is to use another tach. Some shops will have a tach ready with alligator clips just for this, ask them and see if they will let you borrow it, or borrow one off a buddy.

In the event you don?t have access to a shop tach, you?ll have to refer to the manual to check the signal source. The signal is a pulse-positive output that?s provided directly from the stator assembly through the rectifier. A peak-reading voltmeter set to ?positive? and the lowest volt scale will enable you to read any voltage output (on this circuit) from the stator. I have posted a link below for this.

Check the procedure and specifications for your engine, since the inspection point, procedure and wiring are not the same for all outboards. In addition, your ohmmeter can be used to check the continuity of the stator windings, as well as the integrity of the rectifier diodes.

If everything still checks out, you will need to test your rectifier/regulator as per your manual.

http://ww2.tflx.com/pdf/obtach~1.pdf

http://ww2.tflx.com/PDF/99320.pdf

 

[HighTrim]

Re: OMC Tach ID?

That being said, if in fact your tach is dead, you will need to replace it. To state it simply, tachometers read off the alternating pulses from the stator. Any of the leads from the stator charging portion can be used for the signal. The designated tach signal wire is merely attached to one of those. Tachs have rotary switches on the back that set it to different numbers of coils in the charging circuit, times two because there is a positive and negative pulse for each coil for each cycle. Tachs measure pulses. That being said, you need a tach that has the setting that you need designated on the rotary switch.

The BRP tach of the right model comes with a harness that you can plug and play. The Teleflex tachometers offer the harness as well.

http://www.iboats.com/Teleflex_Tacho...-view_id.40245

Or you can easily wire most tachs, that have the correct settings on the rotary dial of course, by either going directly to the ignition switch or by cutting into the main harness.

 

[bralex]

Re: OMC Tach ID?

Thanks for the replies guy! Sorry I didn't respond back promptly but I knew I needed to get proper ID on the current tach which took some time to get done. The tach does in fact operate, but I don't know if it can somehow be off significantly?

The current tach # is 175029 and states that it is for us on 5,6 & 10 pul/rev, alternator equiped outboards and 6 pul/rev OMC Sea Drive engines. Use position 3 for 10 pul/rev.

The new tach # is 175056 and states that it is for use on 2-3-4 pul/rev stern drive inboard and 6 pul/rev outboards and OMC Sea Drive engines.

Since they are both for use in 6 pul/rev engines, would that mean that they are interchangeable?

At WOT my 16' Lowe 1600 runs at 5000 rpm with a 12 1/2 x 15. Seems that it should have more rpm with that prop? The next size down prop is a 12 1/2 X 13 which I would think is a little small? This is what prompted me to consider that tach as the culprit.

 

[bralex]

Re: OMC Tach ID?

Still hoping for a helpful reply! I'm excited about my first fishing trip coming up soon! I'll be taking the boat up to Canada for four days to try my hand at some Northern Pike. There are a few minor items to take care of prior, but this is the most crucial. Thanks in Advance!

 

[bralex]

Re: OMC Tach ID?

Good News! Got positive ID of my tach in the boat. It was indeed a OMC. Went to my local dealer and found out that if it's working, it's fine. "They either work or they don't". The other good thing is the replacement tach will work. They both are 6 pulse models. So as it turns out, I'm in good shape. One working and a original replacement if needed down the road.