Smartcraft temp gauge problems

[bjdunnie]

Hi everyone,

I am experiencing some sort of electrical issue with the port engine and Smartcraft gauges. I have an intermittent issue whereby the temp on gauges (both analogue and digital) fails to read. It will stay that way for between 5 – 10 minutes, and then all of a sudden the temp will show normal /correct operating temp, then without warning it fail again. This only occurs on the port engine. Temp gun suggests that there is no fluctuation in operating temp of the engine. The sensors have been swapped with the other engine and it made no difference.


Whilst down at the boat on Saturday, I happened to notice that the temp gauges came back to life when I touched the button to lift the engine hatch, maybe coincidence, but I tried it on several occasions when the gauges were reading zero, and sure enough, the temp gauges would come back to life. Maybe unrelated, but the port engine is also bad for breaking water PSI sensors – they rarely last for more than a month or so before they fail.


I have swapped the sensors, checked the connections to the gauges and the sensors on the engine and they all seem ok with no sign of corrosion. My gut feel is some sort of grounding problem for the engine, but I don’t really know where to start to investigate that.


Appreciate any advice

 

[Bt Doctur]

In most cases, the system ground (not the negative battery cable)is attached to the motor mounting bracket near the starter or to a bolt on the rear motor mount housing.
If you suspect a grounding issue ,run a jumper from the block to the dash negative buss

 

[jason78]

The Smartcraft Gauges (Digital and Analog) both are displaying information relayed to them by the ECM. If all other readings on your 4-in-1 gauges and Smartcraft Gauges (SC1000 or SystemView, you don't mention what you have) remain stable during the problem window, the problem is most likely between the Sensor and the ECM. So either you have a a bad sensor, a fault in the engine wiring harness or a problem with the ECM. I dont mean to sound insulting but are you sure you swapped the Engine Coolant Temperature Sensors? Just want to make sure as there are various sensors on these engines. If you are sure of that I would look around at the engine harness for any obvious signs of damage.

 

[bjdunnie]

Many thanks for the reply's.

Its the SC1000 that is installed and the other readings on the 4-in-1 gauges and Smartcraft all read fine and remain stable, with the exception of the water pressure which has been an ongoing problem since purchasing the boat - 4 sensors in the last 18 months. The 2 sensors that I mentioned have been swapped are the ones on the thermostat - I think one is the temp sender (left side of t-stat), and one the temp sensor (right side of t-stat).

I will get a chance to go down to the boat later this week, so will have another good look at the wiring harness and the ground connection.

Our boating season is well underway, so I am keen to get these gremlins sorted so that I can worry about keeping the beer cold, and not whether the engine is overheating.

Cheers

 

[jason78]

Many thanks for the reply's.

Its the SC1000 that is installed and the other readings on the 4-in-1 gauges and Smartcraft all read fine and remain stable, with the exception of the water pressure which has been an ongoing problem since purchasing the boat - 4 sensors in the last 18 months. The 2 sensors that I mentioned have been swapped are the ones on the thermostat - I think one is the temp sender (left side of t-stat), and one the temp sensor (right side of t-stat).

I will get a chance to go down to the boat later this week, so will have another good look at the wiring harness and the ground connection.

Our boating season is well underway, so I am keen to get these gremlins sorted so that I can worry about keeping the beer cold, and not whether the engine is overheating.

Cheers

Just want to get clairification. You mentioned the temperature gauge reading in the first post but then mentioned water pressure in the second? Are you also having problems with water pressure sensors or was that a typo?

 

[bjdunnie]

Sorry for the confusion, yes I am also having problems with water pressure readings (ongoing problem for a year or so). I have been replacing the water pressure sensor, and the water psi gauge readings will be correct for a month or so, then the sensor (I assume) is failing and the psi reading on the gauge will sit at 2.75 which is obviously wrong. Local Merc Dealer said the water pressure sensor is notorious for failing. My bit of research on the web suggests that the water pressure sensors seem to be problematic if there is a grounding issue which is what made me initially think there may be a grounding issue also contributing to the issue with the temp gauge readings as well.

Thanks
Brad

 

[jason78]

With that many sensors going bad one after another I think either you have a problem with the ECM or a short in the engine wiring harness. I hate to say it but you are going to probably in for some troubleshooting time. Do you have any Mercruiser Certified Shops that have the equipment to run a proper full diagnostic on your ECM? If not, you may want to consider sending it to Whipple Industries in the US (unless you can find a similar outfit in AU). The ECM will be the easiest to eliminate. If it tests OK, you will need to troubleshoot or replace the engine wiring harness if you cant find a fault. Honestly you may end up cheaper labor wise just replacing the harness if the ECM tests OK. I wish I had better suggestions but it is clearly an issue with one or the other. Have you checked your voltage at the ECM to make sure it is right around 12.5V DC? Weird things happen to ECMs when voltage is low or high.

 

[bjdunnie]

Yes, we have a Mercuiser Certified Service Centre nearby, although before I get them involved, can you please explain how to test the voltage at the ECM as that sounds like something I can tackle before progressing to more expensive alternatives. Thanks

 

[jason78]

Yes, we have a Mercuiser Certified Service Centre nearby, although before I get them involved, can you please explain how to test the voltage at the ECM as that sounds like something I can tackle before progressing to more expensive alternatives. Thanks

The easiest way to is look at the digital voltage reading on the TACH of the engine in question. This will tell you what the ECM is reading. You could also double check the battery bank on that side with a multimeter. You have to be plugged with a scanner to see sensor voltage.

 

[bjdunnie]

Mercruiser Tech booked in - I will let you know how we go. Thanks

 

[jason78]

Mercruiser Tech booked in - I will let you know how we go. Thanks

I honestly think this is the best path. I am all about DIY but is sounds like you are going through sensors left and right. There has to be something deeper. As expensive as sensors are here, I can't imagine what they are costing you.

 

[bjdunnie]

Quick update on an older thread:

Mercury Tech is booked tomorrow to investigate what I thought was some sort of electrical issue causing temp sensors to be problematic, however after weeks of investigation and multiple unsuccessful attempts at solving the issue myself I may have stumbled across the issue:

Service Bulletin MerCruiser SB-2013-05R1

Water Circulation Pump Impeller Cracking

NOTICE
Revised May 2013. This bulletin supersedes the previous bulletin number 2013-05 April 2013.
Models Affected
Models Covered Serial Number
4.3 Liter Models 1A645142–2A036214
5.0, 5.7 and 6.2 Liter Models 1A645061–2A036260

Scope - Worldwide

Situation

Mercury MerCruiser has observed water circulation pump impellers cracking, which can cause the engine to run below normal operating temperatures or cause an engine overheat. These impeller failures sometimes may be difficult to diagnose.
Below are some specific symptoms and actions to help diagnose the potential problem.

Symptoms
All engine models identified above:
Water pump noisy, rattling or emitting a rotating noise.

All engine models with seawater cooling of the engines identified above:

Engine runs below normal operating temperature, and then the thermostat cycles from low temperature up to near thermostat temperature and drops back down. This cycle will repeat multiple times. ECT (Emission Control Technology) engines
may have a time to closed loop fault # 306, which can be observed from the CDS G3 service tool. If the operator continues using the engine with the above described condition, the lack of water circulation in the cylinder block will lead to an engine overheat.

Water Circulation Pump Impeller Cracking

Engine runs at normal operating temperature initially, but as the operator continues using the engine or the engine RPM is elevated with loads increasing, the lack coolant circulation in the cylinder block will lead to an engine overheat

Inspection of Impeller
Confirmation of the impeller cracking without removing the circulation pump from the engine can be accomplished by the
following procedure below.

1. Release the tension on the accessory drive belt.
2. Drain the engine cooling water or glycol so the fluid level is below the circulation pump.
3. Remove the plug on the top side of the circulation pump.
4. Insert a flat blade screwdriver no larger than 0.190 in shaft diameter and at least 5.5 inches long into the forward center inside diameter of the top plug hole at an angle equivalent to the 7 o' clock position, locking into the impeller vanes.
5. Hold the screwdriver in the locked position and rotate the water circulation pump pulley, feeling for resistance against
the screwdriver. If you do not feel resistance, the circulation pump is broken or slipping on the pulley shaft.

I havent experienced the overheating symptoms, but the overcooling is exactly what I am experiencing if the temp gauges are in fact reading correctly. Other than changing the t-stat there is very little commentary on overcooling issues on the internet except for this service bulletin. Generally I dont like telling the mechanics how to do their job, or what I think the issue is, but I did mention that they should bring a new circulation pump with them when they come down to the boat- just in case......

Will give an update once we (hopefully) have sorted the issue. Maybe all this time the the gauges have been correct and the engine temps are actually fluctuating significantly in short bursts, which has made diagnosis, even with a heat gun so problematic

Brad

 

[bjdunnie]

gauge/overcooling problem has been solved.

The gauges were actually fine, there was a large variation in temps actually occurring (30f - 160f) as a result of a failed circulation pump. When the temp bottomed out it looked like the gauges were dead, but they werent. The impeller in the pump was completely gone except for a few corroded bits, which resulted in large volumes of water being passed through the cooling system without regulation. It looks like the pump was replaced at some point by a previous owner with an automotive version, had it been OEM the brass impeller would still have been there, just off its mount.

Water PSI Sensor was replaced under warranty.

Engine wiring was tested and the only problem was a slight voltage drop, most likely due to a bad terminal connection on the wire coming from the back of the alternator which was also fixed.

Boating became a little less frustrating today

Brad