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Ritchard 05-13-2012 10:47 PM

2QM20 Tach wiring
Hi all,

I recently popped a new Faria tachometer into my boat, where previously someone had put a blanking plate.

Can someone help me sort out the wiring leads in my control panel? This is for an alternator signal tach.

The wires are:

I, G, W, and "+"

They should equate, I think, to ignition pos, alt signal, ground, and lamp pos, but my testing today stumped me.

Little help?

Thanks in advance.


Ritchard 05-15-2012 12:34 PM

Re: 2QM20 Tach wiring
Further reading suggests that these might be factory wires for the magnetic tach sender, but I cannot see one on the back of the engine. I guess I am going to have to run a fresh line from the alternator to the tach.

JustinC25 05-15-2012 12:38 PM

Re: 2QM20 Tach wiring
I'm interested to read about your progress. I have a 1978 Endeavour 32 and want to put a tach on my 2QM20 as well. I have seen in diagrams that the transmission has a plug where a tach sender is installed.

Ritchard 05-15-2012 12:59 PM

Re: 2QM20 Tach wiring
I think just running a signal wire will work fine. I am pretty sure there's no magnetic sender, or I'd use the wires as they are. The tach I bought can be fed either magnetic pulse, or alternator signal.

JustinC25 05-15-2012 01:13 PM

Re: 2QM20 Tach wiring
Can you tell me which Faria model number you used? From my previous research, I found we would have to buy the magnetic sender and screw it in to the transmission where there is currently a bolt. Probably pricier than the Faria, but I do wonder if both are just as accurate.

Ritchard 05-15-2012 01:34 PM

Re: 2QM20 Tach wiring
It's a Faria IS0015 Variable Ratio Alternator and Switching Diesel Tachometer. It will be accurate on the alternator, but the problem is you need some kind of reference tachometer to dial it in. I have this cheapo strobe tach to use as a reference to set it up with.

JustinC25 05-18-2012 01:15 PM

Re: 2QM20 Tach wiring
Are you using a tachometer similar to this?
Laser Photo Tachometer measures RPM for Model Airplane Engine Electric Gas Motor | eBay
Do you apply a piece of reflective tape to the engine drive shaft pulley and use that for taking the reading?

I'll take a look at my engine this weekend, but is there already a signal wire on the alternator to connect to?

Thanks, let us know how your install goes.

Ritchard 05-18-2012 01:21 PM

Re: 2QM20 Tach wiring
That's more or less the same thing I have, yes. Stick a piece of reflective tape to the front pulley wheel, and measure the blips. Your alternator should have three wires coming form it, (+), (-), and signal.

I'll probably get this done tomorrow - it's on the jobs list.

Ritchard 05-19-2012 11:00 PM

Re: 2QM20 Tach wiring
I wired it up today, but didn't bring the instruction sheet. The adjustment was a little confusing. Now that I've been able to look at the (not very clear) instructions, I know how to make it work right tomorrow.

JustinC25 05-27-2012 03:34 PM

Re: 2QM20 Tach wiring
Did you get it calibrated? I meant to take a closer look at my alternator yesterday. Is the signal line used for the engine panel light that goes off once the engine is running? Do you have any photos from the installation?

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