Re: [OMC-Boats] Instrument Question (jd)

From: Lee Shuster <lee.k.shuster@...>
Date: Wed, 4 Mar 2009 11:23:37 -0700

As memory serves (my boat's tucked away for the winter) my 307 Chev has the temp sensor located in approximately the same position, up top and front near the thermostat. I ditched the OMC "idiot light" switch for a digital water temp gauge from CruzPro (Model T-30)<>. (Another good source for general instrument/sender info is: ) It's pretty common for US instrument manufacturers to use the Teleflex-marine/Stewart-Warner-auto type sending units for fuel, oil, temp instruments. (Replacing the oil pressure switch with a gauge sending unit (up top but rear on the Chevy) took a 90-degree brass adaptor to clear the distributor.)

Typical Temp Readings: With a 140 F (std) Tstat installed, my digital gauge starts out reading ambient air temps (typically 70 F). I can also compare this to lake water temp on my CruPro SLT-110. After a few minutes of idling at the dock, or slow running it will gradually climb to a normal operating temp of right around 140. (And yes, as Ethan mentioned I checked it's accuracy on the stove with a thermocouple probe and my Fluke DMM). Under aggressive running conditions it climbs into the low-mid 150's. I've got it set to alarm at 175 but it's never gotten near that. I've also observed it climb a little (high 150's) under stretches of reverse-gear operation, when there's not as good a sea-water pickup from the lower unit.

Analog guages are fine as well and are much more revealing than the simple warning lights. I went digital so I could log instrument data via NMEA strings into a laptop or PDA, which I've never gotten around to doing. If I let other people use my boat (which I never do) I would wire the alarms for oil pressure and cooling temp into shutdown relays to prevent engine damage, but I monitor things pretty closely, so I haven't done that.

Lee Shuster
Salt Lake City

From: omc-boats-bounces@... [] On Behalf Of BLDFW
Sent: Wednesday, March 04, 2009 10:21 AM
To: omc-boats@...
Subject: Re: [OMC-Boats] Instrument Question (jd)

On my Buick V6, the water temp switch is up top on the intake manifold below and in front left of the carburator and behind the thermostat housing at the top front of the engine. I just pulled my out yesterday to replace it with a gauge sensor. Same with the oil pressure switch, it's on the left lower front of the block just behind the lower hose connetor.

--- On Wed, 3/4/09, omc-boats-request@... <omc-boats-request@...> wrote:
From: omc-boats-request@... <>
Subject: OMC-Boats Digest, Vol 23, Issue 2
To: omc-boats@...
Date: Wednesday, March 4, 2009, 11:00 AM

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Today's Topics:

   1. Re: Instrument Question (Ethan Brodsky)
   2. Re: Instrument Question (jd)

On Mon, 2 Mar 2009, jd wrote:
> As far as the water sending unit, another interesting point you
> raise. I am wondering if mine is even in the spot it's supposed to
> be. That could be contributing to weirdness.

I can't recall where the temp sensor is on my 225, but I would generally
say that a water temp sensor should be in the engine's internal cooling
loop (the portion that has water cycling through it even when the
thermostat is closed). Typically this is near the thermostat, though
anywhere in the cylinder water jacket should be reasonable,
Received on Wednesday, 4 March 2009

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