Communication issues with 8.1’s

PlayDate said:
If I follow what Tom says and look at the videos....it would appear that you are losing power on the Red and Black wires which in turn causes the display to turn on and off.
Can you put a voltmeter on the red/black wires and see if power drops?

Tom, where is the power supply for his Smartcraft system and what voltage should he see on those wires?
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Smartcraft power is from the engine's electrical harness. Most late engine arrangements have a 14 pin round connector which is the Smartcraft primary connector; from that connector are the 10 pin square Smartcraft connectors. Two of those pins are the network's power. Specifically where that power is sourced on the engine? I don't know but there is always a fuse.
 
ttmott said:
Smartcraft power is from the engine's electrical harness. Most late engine arrangements have a 14 pin round connector which is the Smartcraft primary connector; from that connector are the 10 pin square Smartcraft connectors. Two of those pins are the network's power. Specifically where that power is sourced on the engine? I don't know but there is always a fuse.
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The videos look like the power is dropping on and off to the system. It could be a number of things but I would start with the input power to the smart craft system and see if that 12 volts is wonky.
 
Thank you, I will start looking there with a volt meter. Would that also explain the drop in RPM when the fault happens? What about disconnecting smart craft at the helm?

Really appreciate your help!
 
Three Seasons said:
Thank you, I will start looking there with a volt meter. Would that also explain the drop in RPM when the fault happens? What about disconnecting smart craft at the helm?

Really appreciate your help!
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So the Smartcraft network has nothing to do with the engine's operation or performance; they are independent.
If, however, there is a simultaneous change in engine performance and a fault in the Smartcraft network then look to the source that provides power to both. Main power to all systems are typically through a Purple/red stripe wire on the engine harness. Most source for power on that wire is the Bat + terminal on the starting motor. Usually, also there is a robust fuse or fusable link between that terminal and wire.
 
Three Seasons said:
Thank you, I will start looking there with a volt meter. Would that also explain the drop in RPM when the fault happens? What about disconnecting smart craft at the helm?

Really appreciate your help!
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I have seen this before but it was not on a Smartcraft display. The main power wire to that system had been spliced for another piece of electronics and that connection became unstable causing the power to intermittently drop. It was really difficult to find but when I found it .....it was obvious.

I would start by isolating the 12 volt feed to the Smartcraft system and putting the meter on it. Within about 10 seconds or so you will know if that feed is the problem. If the meter drops in synch with the display.....then you have found the source of the problem. To confirm it......run a known 12 volt jump wire to the + wire. If it still cuts out, you have a bad ground. To confirm that, run a known ground jumper to the - wire.



If the input voltage to the Smartcraft system remains stable and the display continues to cycle on/off.....then we can move on to diagnosing the Smartcraft system.
 
First off you have an excellent owner's manual complete with Smartcraft wiring diagrams.

https://owners-resources.searayweb.com/owners-manuals-files/2006_38 Sundancer_38 Sundancer.pdf

Of particular note.....is the power for the system which in part comes from the port/starboards key switches... top of Page 115. Then there is the very detailed page 135 which shows the Smartcraft cable layout for your boat.

My starting point would be testing the wires going to the Smartcraft keyswitch connector. Operating on the assumption that we have an intermittent power supply issue with the Smartcraft system. It makes the most sense to look there. Recognizing that both sides are failing at the same time makes the problem a bit more interesting since the port and starboard sides appear to be isolated from each other. Make sure the Smartcraft system is properly grounded. A loose/bad ground would definitely cause both sides to drop at the same time.

As you locate and disconnect these connectors....make sure they are not corroded and they seal together properly.

Has anyone added any electronics or done electronics work to the helm prior to this problem showing up?
 
Three Seasons said:
Hi Captlori,
Hoping you survived your last bout with Covid from last fall. Have you installed cables yet? Our boat went in one week ago, faulted only three times the first day and 30+ times two days later.

This is so incredibly frustrating - still looking for answers - during winter we tested my 8.1 PCM’s on another boat and they never failed also cleaned more cables + & - on everything. Next maybe inspect &/or replace cool fuels (because in was running weird) and replace cables if it works for you.

Thanks
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Yes survived covid thanks. I haven't replaced cables yet as our weather has been bad. Cold in 40's and/ or raining . I have the cable and hoping with weather, should have it in the next few weeks. I also was told in 2019 to replace ECM. I did that but it came back. Very expensive non-fix. Hoping with more people having this issue we find fix soon. Come on spring weather. Lori
 
Great to hear…

Don’t know if you saw my earlier post, we moved my PCM’s to another boat with 8.1s and they worked perfectly. Going to take a deep dive into ttmott & PlayDates recommendations this week-end.

I’ll keep you in the loop.
Thanks
 
Three Seasons said:
Great to hear…

Don’t know if you saw my earlier post, we moved my PCM’s to another boat with 8.1s and they worked perfectly. Going to take a deep dive into ttmott & PlayDates recommendations this week-end.

I’ll keep you in the loop.
Thanks
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Just curious, did you put his PCM into your boat and what happened?
 
While I agree with @ttmott nothing in SmartCraft send control signals to the ECM I’m not sure the SmartCraft power or CAN buss is completely isolated.
If the power is grounding out intermittently like chafing on a screw or such it might be confusing the ECM.
Same for the CAN buss.

The SmartCraft is not needed it’s an option. Have you tried just unplugging it at the engine and see if the issue goes away?
 
Chased this problem before. Check the Starter cable on starters. (comes from your battery switchs) If it is loose (this is where all 12v power for pcm and engine power starts from. if loose it will randomly drop and give all kinds of issues.
 
Tri County Trail said:
Chased this problem before. Check the Starter cable on starters. (comes from your battery switchs) If it is loose (this is where all 12v power for pcm and engine power starts from. if loose it will randomly drop and give all kinds of issues.
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Late to the party here, but this and ensuring that both that connection and the main engine ground from the block to the battery are very corrosion free, clean, tight and protected is of the utmost importance.
 
If you look at the wiring diagrams you will see that the SmartCraft system is isolated at least from a + wire perspective. It shares the same ground circuit where the problem may lie.

If you watch the videos.....either the + or - is dropping out causing both sides of the display to go dark. That is not a CAN bus signal issue.

The fact that the engines continue to run reinforces that the SmartCraft system has a power supply issue which hopefully will reveal itself soon.
 
Worked on the boat yesterday on the water with our awesome marine Technician. Sad to say with did not find the fix but identified exactly what is happening. We got several engine fail recordings on the laptop and will send those files to Mercury for further evaluation. This issue mostly occurs under load so I drove the boat at about 1600 RPM with the engine hatch open and the Tech at the motor. We isolated the issue to be only on the Starboard motor and as I said earlier the motor starts and runs perfectly except when it fails. The failure is like turning the key on-off really fast and because strb runs SmartCraft and gauges it make all helm readouts on-off crazy. The on-off also creates the RPM surge -/+400 RPM.

We have ruled out the following…
-Swapped PCM’s and the issue stayed on the Strb motor
-Fuel PSI stable - I recall 40
-all plugs and wires good
-disconnected SmartCraft data cables to helm - no change (Thank you ttmott )
-swapped all relays from Port to Strb - no change
-installed Merc remote starting units (with keys & horns) - no change
-metered all 12volt systems and they are ok except when on/off happens volts drop.
-cleaned all grounds and +/- connections at on starter.
-disconnected Engine sink controller in bilge

I could be missing a couple other checks but we think the issue is on the Strb motor wire harness, we moved the harness a lot and could not duplicate the on/off. The on/off now happens on the average of 25 times every 3 to 5 minutes with no consistency, one time it did not fail for 20 minutes we thought we were on to something BUT NOT.

So thats where we are…somehow I feel better about it but still frustrated its not fixed HOPE we are getting closer.

Thank you all for helping, I will keep this updated and really appreciate your further input.
 
Ground lugs verified - Check
Wire crimps - In the power connectors you might have to pull the pins and sockets out and verify the crimps. Also inspect all of the ring terminal crimps. A marginal crimp or that insidious corrosion you can't see.
As this intermittence affects both the engine's performance and the Smartcraft system it has to be a common power supply issue.
 
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