Re: [OMC-Boats] Instrument Question

On Mon, 2 Mar 2009, BLDFW wrote:

> I have a '70 Explorer that I am updating the instrumentation on.  I've
> acquired a Faria six gauge set that includes an oil pressure and water
> temperature gauge that both require sending units.   At the moment, I'm
> having a bit of a challenge breaking the switches from the engine to take
> with me.  The local car parts place, AutoZone, has no clue on what to do
> if you can't give them a specific car make and model and get totally
> flustered you say it's from a boat to the point of my being leary of
> taking any part they can come up with. Has anyone replaced the existing
> switches with sending units?  Any suggestions on the right units; part
> numbers, etc?

I have written down in some notes from a few years back that the original
OMC dash oil pressure/water temp gauge was OMC part #172075, and the
senders were #172127 (oil pressure) and #171960 (water temp).

However, the key point here is to get senders matched to your Faria gauge -
it's easy to make the gauges plug in mechanically (they're likely have NPT
threads of some sort), but the electrical characteristics must be the same.
The OMC senders will plug into the engine, but many not provide appropriate
readings on your gauges.

So I'd call Faria, check their website, stop at your local dealer, or look
at the manual for the gauges you found - they should recommend a compatible
sender.

I would assume you have a "Faria Water/Oil Temperature Gauge" - they
recommend their temp sender, which comes in 1/8 NPT. The OMC engine likely
has 1/4 NPT, so you'll just need an adapter - you can get it at a hardware
store. I'd probably try to buy a brass one instead of steel or cast iron
so it doesn't rust - if you have trouble finding that, Faria likely stocks
them as well or you could try West Marine, but it'll cost way more than a
hardware store. The specs for the gauge are online here:
  http://faria-instruments.com/site_manuals/IS0007E.pdf

The oil pressure is a bit more complicated - there's different combinations
of senders depending on which gauge you have:
  http://faria-instruments.com/site_manuals/IS0002F.pdf
I'd guess you want the single-station american common ground one, but it
depends on what gauge they're actually selling. Call them at the number
listed in the document and ask.

All their manuals are online here:
  http://www.faria-instruments.com/downloads.php

If you can find out the actual resistance specifications their gauges are
looking for, then you can use much cheaper autmotive parts instead, but
this will likely take some time. Call Faria and ask for the resistance
specs their gauge requires (i.e. "450 ohms at 120 F, 900 ohms at 180 F"),
or better yet, ask them for the original manufacturer's part number for
their gauges (they must be hesistant to give you the part number, as they
likely mark the gauges up significantly, but you can usually get it out of
them with some persistence). Then call the manufacturer (which will likely
be in Europe) and ask for a list of US autotmotive applications it's used
in (they'll claim it's confidential information, but usually can be talked
into revealing it).

Ethan

-- 
<a href="http://www.engr.wisc.edu/~brodskye/"> Ethan Brodsky </a>