SmartCraft Alarms - OVERSPEED, Port and stbd EMCT OVRHT.

[rondds]

Engine: 2007 Merc 8.1s, 314 hours

The past two times I had the boat out (two separate days), when coming off plane after running at cruise (~3400RPM), I got an alarm on the old style banner LCD SmartCraft display and on the Garmin MFD (connected to the engine PCM). Both displays basically say "Check Stbd Engine" (no help). Engine went into Guardian mode for several seconds and reverted to normal on it's own.

Each time this happened, the engine temps on the analog gauges were right at 170, the temps on the Garmin (MFD) were 176 first time, 168 second time. No interruption in water flow either time. First time I jumped in the ER as quickly as I could raise the hatch, with my wife running the boat at idle speed, with my handy-dandy IR temp gun and shot all normal readings (elbows, therm housing, manifolds, transmission, whatever I could (keep in mind, the alarm message was ambiguous so I didn't know exactly what I was looking for).

Connected the laptop to the starboard engine and ran the Diacom software after both of these occasions. Both times I got an OVERSPEED, a STBD EMCT OVRHT (exhaust manifold coolant temp overheat) and a PORT EMCT OVRHT. After the first incident, I did clear the codes from the ECM after the Sept 10 event, so the Sept 24 codes are new.

This explains what the code abbreviations stand for...

Mercruiser Alarm and Fault Codes

I won't bore you with the full reports, but in a nutshell, here's some pertinent results

Sept 10 alarm
Battery Volts - 13.52v
engine hours - 312.13
manifold air temp - 136.4
coolant temp - 176
engine speed 1026 rpm
Guardian Strategy - 23 seconds
Overspeed - 15 seconds

Sept 24 Alarm
Battery Volts - 14.3v
engine hours - 313.73
manifold air temp - 118.4
coolant temp - 168.80
engine speed 966 rpm
Guardian Strategy - 64 seconds
Overspeed - 8 seconds

I included the battery voltage in the above results b/c after doing some searching it seems it could be related to low voltage or alternator problems.

Note that the OVHT alarms, according to the Merc Code/Fault explanation, would require 212* to trigger (unless I'm reading that wrong).

There are sensors on the port manifold and on the starboard manifold. Interestingly, they read the exact same temp at the exact same time. Very unlikely both manifolds run at the same temp. But, again, the temps are not "alarming," though they triggered an alarm. Weird.

The ONLY temp readings that the report gives are the ones I listed above. ie: there are NO readings titled "EMCT TEMP" in the reports.

I did NOT have to shut down the engine to reset and get out of Guardian mode. Cleared itself.

Seems that OVERSPEED and EMCT OVRHT go hand in hand.

There was clearly no overspeed occurence since both times, this was coming out of normal cruise speed (not coming up on plane), and the rpm readings grabbed at the time of the alarm would indicate that there was actually no overspeed event.

Spoke to some bright people on this message board about it and the consensus was that these things happen to every engine but until the advent of ECMs and PCMs and and fault codes and smart-alarms, they've gone largely unnoticed. I'm not overly concerned about the issue, but, this engine could be trying to tell me something and getting an alarm when coming off plane each time is a PITA. Boat is going to bed very soon. I will likely just run the engines to heat up the oil for changing, and take a 4 min idle over to the travellift on the morning of Oct 7th.

Any ideas folks??

 

[scoflaw]

Coming off plane is when the temps spike. Even though the temp reading at the t stat housing is within range, you don't know how hot it is in the exhaust coolant.

I myself would be looking at the manifolds and elbows.

 

[rondds]

Scof...thanks. Seems that the sensors that trigger this alarm are actually IN the manifolds. So they are reading temp right at that spot. There is also a sensor in the therm housing, but that one is not the one triggering the alarm.

Also, the Temps at the very moment of the alarm are captured in the report, down to the 100th of an hour. Highest temp was 176.

With all that in mind, I'm leaning towards a bad sensor OR compromised cooling. I'm going to pull the HE end caps and take a look. MaybE a nice system-wide acid bath too. Worst case scenario, I may need to think about some new cast iron components.

Impellers are new this spring. Flow is very good.

Question...how hot should discharge water be. It's not scalding bit it's very hot to the touch.

 

[scoflaw]

Like you say, the EMCT is triggering the alarm, But the 176 degree # can't be associated with that sensor.. Which makes sense, I would think that the exhaust water would be hotter than that and that temp sounds more like the circulatory engine temp.

 

[paulswagelock]

I had that error last year. It was from insufficient cooling water flow in the manifolds.
my inlet hose and plastic sleeve were partially collapsed restricting flow.

 

[rondds]

Paul, I would certainly expect an alarm with a condition of insufficient cooling water, but in my case, b/c the temp reported by the sensor in the manifold at the precise moment of the alarm was 176 1st time, 168 degrees 2nd time. So, in fact there seems to have NOT been any overheat, though the alarm said there was one. And it seems the sensor isn't supposed to trigger an alarm until 212*

 

[SeadawgVB]

Ron, did you ever find a resolution to this issue?

Dave O.

 

[rondds]

Dave
Not yet. Boat came out for the winter shortly after this problem manifested. I did buy all the components to replace the manifolds and the sensor on that motor. All that will be installed at the end of this month but boat won't be afloat until late April for a seatrial. Stay tuned!

 

[rondds]

Follow up...
Replaced the manifolds and riser blocks, as well as the temp sensor contained there-in. All's well now.
I'm thinking it was the sensor as there wasn't that much crud in the manifolds that could cause enough of a temp spike to trigger the sensor. But who knows for sure...

 

[scoflaw]

Too many things to go wrong with Smart Craft. Gets your blood pressure up and your wallet out. This will be my last boat with SC. Analog worked well for many years, KISS

 

[kysearay]

Follow up...
Replaced the manifolds and riser blocks, as well as the temp sensor contained there-in. All's well now.
I'm thinking it was the sensor as there wasn't that much crud in the manifolds that could cause enough of a temp spike to trigger the sensor. But who knows for sure...

Ron
How is the boat running, this just happened to me last weekend - exactly the same situation - really got me by surprise. Mine is going in for injectors and major clean out and need to know if I am adding this to the growing list of "issues" that I will be addressing?
Thanks
chris

 

[rondds]

Chris
Running great and hasn't happened again. Was your boat always in freshwater? If so you won't have the amount of crap I had in my manifolds. Not sure what the lifespan of these things are in fresh water.

 

[kysearay]

Chris
Running great and hasn't happened again. Was your boat always in freshwater? If so you won't have the amount of crap I had in my manifolds. Not sure what the lifespan of these things are in fresh water.

Thank you Ron,
Yes freshwater boat -is it worth replacing manifolds or maybe just a bad sensor??
Kind of ticking me off with paint in the injectors and now this one. Also having "louder" backlash on the gear box at low idle - once idle kicks up the "banging" is gone - have had a couple mech look at and now thinking is that its just normal backlash noise in the drive???
thanks
chris

BTW - dentistry?