FL-120, Water Temp when off > 170 degrees F

[BruceK]

You'll probably find out more by swapping the two thermostats.
Or just replacing the low reading thermostat.

Swapping thermostats involves removing the header tanks they sit under.
For me, one engine reading high turned out to be just the FB wiring.
ADC may recommend replacing the raw water pumps with an updated version that does not have the drive fail without warning (about $500 each).
There is a metal tube in the header tank which blocks up and needs drilling clean. Probably unrelated to this.
Sometimes concentrating on trying to help we get a bit "direct'. Rarely someone actually gets nasty, that`s not happening here. Exasperation with a problem can be sensitizing too. I hope you solve the problem.

Detailed discussions about correctly pronouncing "pedant" can be had.

 

[catalinajack]

When I installed new gauges on both helms I ran new wires thus eliminating any possible problems that might be lurking in the original runs.

Hi JB, Like others here - when screwing around with boats - my experience - there is always something!!


If it's electrical or electronics - it's most likely corrosion or loose connections. Water, vibration and electricity don't play nicely together!


So as not to appear "pedantic" or condescending I'm gonna give you my best quess as to the problem in short form. There are technical ways to prove it but that would take a lot of typing.


To wit: There is corrosion in the temp sensor mounting hole. Remove, clean, grease, check resistance of sensor (300 to 800 ohms), reinstall(no teflon or other sealing tape)

 

[Comodave]

When I installed new gauges on both helms I ran new wires thus eliminating any possible problems that might be lurking in the original runs.

Absolutely. Also you can go with a continuous wire rather than having connectors to reduce the possibility of future loose and/or corroded connections.

 

[SteveK]

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I've seen people speak with great authority about parts on a FL that aren't there.

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Now that qualifies to be called pedantic

 

[DW1979OA]

I learn a lot from the forum members. This is a device recommended by more then several contributors. I recently installed a device from Borel Mfg that monitors the exhaust temperature, and sends an alarm if the temp shoots up. This could be caused by a failing impeller or some sort of blocked raw water. This device reacts well before your water temp gauges do, and could possibly save your engine from an extreme overheat situation. It is a temperature sensor that straps on to the exhaust hose where it leave the elbow and if it senses high temperature, it sets off an alarm.
I installed it on both mains, the generator, and opted for the additional Hi Bilge alarm too.
As boat options go, this was relatively easy to install and inexpensive. Hope I never need it, but have it alarmed to both the pilot house and the fly bridge to give me advance warning.

 

[Comodave]

+1 on the Borel system. I have exhaust temperature sensors on the mains, Water in Fuel (WIF) and 2 high water alarms. Very easy install, consumes no power unless there is an alarm. Highly recommended. No affiliation.

 

[Fr8dog61]

. …it seems every time I "solve" a problem it uncovers a new one. The survey missed a lot.

Large boats are highly complex pieces of machinery, with many complex systems and rarely, if ever will all those systems be functioning 100% correctly. Learning what is normal is part of the fun. :lol:

 

[Nick F]

I too am annoyed by temperature gage inaccuracy and am planning to "calibrate" my temperature gage, or change to a more accurate system.

First a few words about how the originally supplied gages work. If the pointer does not go to zero when ignition is off then you (like me) have the Stewart Warner type. The pointer has a magnet on it which aligns with a magnetic field generated by the combined effect of a couple of coils. The sender is in series with one of these coils. As the temperature varies the resistance of the sender varies (something like 400 ohms when cold to 40 ohms when hot with a very non-linear relationship). This causes the magnetic field to change direction somewhat, with the pointer following it.

The advantage of this system is that it is insensitive to the supply voltage. It is also a very basic system (no electronics) and hence very reliable within its limitations.

Disadvantages are:
- poor accuracy
- the pointer does not go to zero when ignition is off (this always bugs me)
- the angle the pointer moves through is very limited - about 60°. Compare this with a mechanical pressure gage which has a pointer movement of about 270°.

As regards the wiring being the cause of a problem, I personally think that bad connections could cause problems but highly unlikely to be the wires themselves unless the gage is very far from the sender (over 100ft, say).

Another consideration is whether the gage reading is repeatable - does it always show the same reading when your engine is at, say, 170F? I suspect that this type has quite good repeatability with the only possible causes of differences being friction in the pointer bearings or intermittent bad connections in the wiring.

Manufacturing variations in the gage and in the sender would cause constant (repeatable) inaccuracies. I am considering adjusting my temperature gage to read correctly at 170F by adding a fixed resistor in series (or in parallel) with the sender. I would find the required value by trial and error and locate it at the back of the gage. Not sure if this will work - its just an idea I would like to try.

Alternatively, there may be other gage systems available which use electronics and are more accurate - however one might be trading reliability for sophistication.

Comments?
Nick

 

[sbman]

I too am annoyed by temperature gage inaccuracy and am planning to "calibrate" my temperature gage, or change to a more accurate system.
...
Manufacturing variations in the gage and in the sender would cause constant (repeatable) inaccuracies. I am considering adjusting my temperature gage to read correctly at 170F by adding a fixed resistor in series (or in parallel) with the sender. I would find the required value by trial and error and locate it at the back of the gage. Not sure if this will work - its just an idea I would like to try.

If the gauge is repeatable for 170 as you think it might be that could be reasonable solution. You can get a decade box to quickly determine the value you need and they aren't very expensive.

https://www.amazon.com/Elenco-Resistance-Substitution-Range-Precision/dp/B0002KX76M

I added an Alba-Combi analog-digital N2K converter box to a pair of FL-120 with Stewart warner gauges. I piggybacked onto the existing gauges and calibrated the digital system by putting the sensors in a cup of hot water with an accurate dial thermometer in it. As the temp of the cup of water fell I recorded calibration points in the digital system and noted the indications on the needle. What I found was that the sender was very linear and repeatable. The analog gauge was repeatable but not very accurate at all, off by as much as 30 degrees. The calibration curve in the digital system ended up being a straight line after taking measurements every 10 degrees from 180 down to 100 degrees.

 

[Nick F]

Hi SBMan,
Are you saying that you had the temperature sender connected to the S-W gage and the Albi-Combi system at the same time? I dont think this would work well, but am curious to know your experience.

I am surprised that you found the sender resistance to be linear with temperature. Most senders use what is called an "NTC" resistor (Negative Temperature Coefficient). As the name implies, the resistance of these get lower at higher temperatures - the opposite of "normal resistive" behaviour. The advantage is that the resistance varies much more than "normal resistive" materials and so can be used to drive fairly crude instruments. Disadvantage is that NTC resistors have a very non-linear characteristic.

If anyone is interested, here are a couple of links which show this:

Oil Pressure and Water Temperature Sender resistance values? - Boat Talk - Chaparral Boats Owners Club

https://www.google.com/search?q=10k...ECAIQAw&biw=1366&bih=657#imgrc=vIi--q23uHsWvM

Since we are on the subject (and at risk of boring you), laboratory accuracy temperature measurements at these reasonable temperature levels are generally done using a sensor resistor made of platinum wire. Platinum is used because it does not oxidise, which could change its base resistance over time. The change in resistance from 175F to 200F is 4% - by comparison, the NTC resistor changes in the range of 40%. The platinum resistor (called a Pt RTD) also requires 4 wires to the sensor to eliminate errors due to the resistance of the wiring between sender and gage.
Yet a third temperature method uses thermocouples and is normally reserved for very high temperature measurements and has its own set of disadvantages. Thermocouples are used on some large diesel engine exhausts (one per cylinder).

Nick

 

[sbman]

Nick,

Yes I have the alba combi connected to the sensors at the helm station. We moved the lower helm station into the engine room and eliminated the upper helm station entirelyl. This required new senders to with resistances that are compatible with the single station, so we installed the single station senders on the engines. The gauges are the original ones from 1967. We have found it to work reliably. I am able to calibrate the alba combi independently of the analog gauges so the digital readings are accurate while the analog gauges are showing what they always did.

I may remember the calibration incorrectly but I am pretty sure the voltage curve was flat from 100-180. I suppose this does not mean that the resistance was linear since it's also interacting with the gauge, I didn't analyze the circuit to that degree and I wasn't measuring the resistance directly, just the voltage signal present at the gauge.

I've worked with thermocouples but don't have any experience with the platinum wire style of temperature probes. Thermocouples can be challenging due to the very low voltages that are created by the probe.

Hi SBMan,
Are you saying that you had the temperature sender connected to the S-W gage and the Albi-Combi system at the same time? I dont think this would work well, but am curious to know your experience.

I am surprised that you found the sender resistance to be linear with temperature. Most senders use what is called an "NTC" resistor (Negative Temperature Coefficient). As the name implies, the resistance of these get lower at higher temperatures - the opposite of "normal resistive" behaviour. The advantage is that the resistance varies much more than "normal resistive" materials and so can be used to drive fairly crude instruments. Disadvantage is that NTC resistors have a very non-linear characteristic.

If anyone is interested, here are a couple of links which show this:

Oil Pressure and Water Temperature Sender resistance values? - Boat Talk - Chaparral Boats Owners Club

https://www.google.com/search?q=10k...ECAIQAw&biw=1366&bih=657#imgrc=vIi--q23uHsWvM

Since we are on the subject (and at risk of boring you), laboratory accuracy temperature measurements at these reasonable temperature levels are generally done using a sensor resistor made of platinum wire. Platinum is used because it does not oxidise, which could change its base resistance over time. The change in resistance from 175F to 200F is 4% - by comparison, the NTC resistor changes in the range of 40%. The platinum resistor (called a Pt RTD) also requires 4 wires to the sensor to eliminate errors due to the resistance of the wiring between sender and gage.
Yet a third temperature method uses thermocouples and is normally reserved for very high temperature measurements and has its own set of disadvantages. Thermocouples are used on some large diesel engine exhausts (one per cylinder).

Nick

 

[Nick F]

Nick,
I am able to calibrate the alba combi independently of the analog gauges so the digital readings are accurate while the analog gauges are showing what they always did.

Interesting - thanks for this. Theoretically, the voltage you are reading off the sensor will also vary with the battery voltage. Have you noticed the readings change when idling? Or maybe your alternator maintains the 13.5 volts charging voltage even when idling. If battery voltage drops I would expect the Albi indicated temperature to increase a bit.

Nick

 

[sbman]

Nick,
I am able to calibrate the alba combi independently of the analog gauges so the digital readings are accurate while the analog gauges are showing what they always did.

Interesting - thanks for this. Theoretically, the voltage you are reading off the sensor will also vary with the battery voltage. Have you noticed the readings change when idling? Or maybe your alternator maintains the 13.5 volts charging voltage even when idling. If battery voltage drops I would expect the Albi indicated temperature to increase a bit.

Nick

The Alba combi can use a reference voltage to compensate for system voltage changes and it does a good job with that. The only thing I didn't like about the abla combi is poor documentation and very slow support. Once I figured it out, it's a nice unit. The N2K data goes to a set of Simrad displays.

 

[Nick F]

The Alba combi can use a reference voltage to compensate for system voltage changes and it does a good job with that. The only thing I didn't like about the abla combi is poor documentation and very slow support. Once I figured it out, it's a nice unit. The N2K data goes to a set of Simrad displays.

sbman:
Thats very slick (voltage reference/compensation). So you can piggyback the Albi-Combi system on top of the basic system. Interesting option.
What are you using to display the temperature?
Nick