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post #1 of 12 Old 07-05-2010 Thread Starter
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Water Temp Install

I wanted to install a water temp gauge and I remember Larry saying he installed one on his 3GM30F with a Tee. But when I went to install there was no way to turn on a Tee due to a cast flange on the pump. If I installed a nipple to get past the flange it would run into the alternator. I installed on the return line but this doesn't give the best reading as you would expect. Larry, what am I missing? Any suggestions appreciated.

In the first photo you can see the idiot light sender is on the output.
In the second photo you can see the flange just below the output hose.
The third photo is my new analog sender on the Tee which replaced the elbow.



Steve
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post #2 of 12 Old 07-06-2010
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Steve,

I think you solved the problem nicely! It should not matter, inlet or return, as long as the system is full and you learn what temp is normal for you. The temp holds rock solid under all loads so if it gets high, you have problem. As I recall, I did the same thing.
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post #3 of 12 Old 07-06-2010 Thread Starter
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Thanks Larry - glad you're still on the list as you contribute a lot of good advice. I hope to motor the Erie Canal from Great Lakes to the Hudson so I wanted to have a better handle on the engine water temp. Your idea of using the Tee was a good one so I could keep the buzzer in the cockpit but I was distraught that I couldn't figure out how to get it on the output.

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post #4 of 12 Old 07-08-2010
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Steve,
I have the same setup for the temp gauge sensor on my boat. I think this type of hook up is very slow in response, as you are reading temp on the inlet side from the reservoir, not the heat exchanger.
On a recent trip the idiot light and buzzer went off, indicating high coolant temp, however the temp gauge did not move. After shutting down and inspecting, I noticed that the fresh water pump had worn out, and leaked coolant around the pulley shaft. The system was almost empty, but the reservoir still had plenty of coolant. My theory is, that while the pump was not moving much coolant, there was still a slow flow from the reservoir, keeping the sensor for the gauge cooler than the idiot light sensor, that is mounted right on the outlet flange to the heat exchanger. So there will be quite a delay in reacting to temp changes with this hook-up. I am not quite sure how to solve this problem, but there is a plug in the pump housing( to the left of your "in" arrow). Is there enough room to make it work?
I do not trust my gauge(btw, both gauge and sensor are working correctly) anymore,and will think of a better way to install the sensor. Right now it is nothing more than an "idiot gauge", that doesn't move.
If you prefer the gauge over the light/ buzzer, just swap out the sensors, and rely on the gauge. Drawback: constantly having to watch the gauge.
Bernd
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post #5 of 12 Old 07-08-2010 Thread Starter
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Unfortunately your experience confirms my suspicions. If I understand the coolant diagrams, there'd be no coolant circulating in the hot water heater loop when the engine coolant temp exceeds 185F as the thermostat closes this loop and uses only the seawater heat exchanger. (Otherwise the water heater would soon blow it's temperature pop off valve). That's why the idiot sender is located prior to the thermostat.

I searched for a sender that would be both analog and digital to no avail as I think the idiot buzzer sender is necessary since anyone's attention can be easily diverted. With our analog sender location what we now have is a gauge to show when the shower's hot.

I looked at replacing the idiot sender with the Teleflex analog sender into the Cruz T30 as it has a built-in 85dB alarm. That's what I'll probably do but their gauges are kind of klunky.

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post #6 of 12 Old 07-08-2010
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Not all true

While I am sure your details are correct, I can tell you that my gauge saved my bacon several times. In one case my heat exchanger was fouled, in the other my seawater inlet was plugged with grass. In those instances the gauge told me I had a problem long before I got to an alarm and I was able to throttle back and limp home. The point is that if you know what is normal the gauge will tell you when you are deviating from normal long before the alarm. I would never have been able to diagnose the heat exchanger problem before a failure without the gauge. In an acute failure of a component, it probably does not reflect that accurately, but that is where an alarm comes in.
Larry
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post #7 of 12 Old 07-08-2010 Thread Starter
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In my post I was misleading when I said "thermostat closes this loop and uses only the seawater heat exchanger". Actually I expect the thermostat is normally closed and water circulates to the hot water heater. When the temp rises (around 185F) the thermostat would open and both routes (to water heater and to engine seawater heat exchanger) are open. The coolant takes the path of least resistance which would normally be the heat exchanger.

However if the heat exchanger were clogged as in the case above the coolant would continue to flow to the water heater in sufficient quantity as you noted.

I was a bit flippant when I said it was simply a gauge to note when the shower was ready and it can serve a useful purpose. Sadly it's not what I really wanted.

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post #8 of 12 Old 07-08-2010
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Steve,
I see you have a 185 degree thermostat. i am thinking of upping mine to 180. hows does this affect the temp in your water heater? Does it get too hot or cause the relief valve to open? My engine is a Universal M-12 and the water heater is a raritan

I also sent you a PM on this.

Last edited by jackytdunaway; 07-08-2010 at 12:47 PM.
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post #9 of 12 Old 07-08-2010 Thread Starter
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I don't know what my thermostat temp is - I was making an uneducated guess.

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post #10 of 12 Old 07-08-2010
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but your engine runs at 185, right. What does that do to the temp in the wqater heater after running for a few hours
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