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SmartCraft Wiring Difficulty with Twin Engines? Any Ideas?

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SmartCraft Wiring Difficulty with Twin Engines? Any Ideas?

Old 07-11-2012, 05:18 PM
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Default SmartCraft Wiring Difficulty with Twin Engines? Any Ideas?

Twin 2007 Optimax 150s, Smartcraft Gauges and wiring harness.
Two Tachs, one Speedometer, volt and water pressure assist gauges for each engine.

The two Perko Off/1/2/All battery switches are wired so that in position 1 each motor is supplied by it's own battery. Moving either switch to the 2 position allows that motor to utilize the opposite battery.

Now comes the "difficulty".
Port engine battery switch in the 1 position.
If the starboard battery switch is turned Off, the port engine gauges will not turn on with the ignition switch, nor will it start.
Turn the starboard battery switch to 1, 2, All, with the port switch to 1, then the port engine will work correctly.

It does not have the same effect in reverse. If the port switch is Off, the starboard engine will start as long as starboard switch is in 1,2, or All.

The problem appears to be in the SmartCraft wiring harness.
According to the schematic I have in hand there is a paragraph that says..

"Wiring Disconect for Multiple engines with single can bus
Each CAN bus must be only powered from one engine. On dual engine installations using a common CAN Bus, the CAN Bus power (3 wire) connector on one of the engines must be disconnected. The CAN Bus power connector is located in the engine wiring approximately 3 in. from the SmartCraft Harness connector. Seal both ends of the power connector with caps. On tripple engine installations, the CAN Bus power connector must be disconnected on 2 engines. "

After operating the boat for a year, one day I was going to flush my engines at my house. I decided to turn the starboard battery switch off while I ran just the port engine. The port engine had no power. I discovered turning the starboard switch to the 1 postion (where I have had it for a year) all seemed to work correctly.

I had my long-time mech come over and view the situation. He double checked the switch wiring and said it is as he has been wiring them for years, and all checks out OK at the switches. However, the port gauges should not come on when only the starboard key is on, which they do, as well as starboard gauges come on when port key is on. So, there is a possible problem in the wiring harness.

He talked to Merc Tech support and they suggested we needed a 2nd CAN Bus, and a couple of crossover wires to make the gauges work correctly.

We installed the above parts and now, when I turn on the port key, the port Tach and two assist gauges come on. The Speedometer does not, but that was explained by Merc Tech that the Speedometer could only be wired to one tach gauge and we chose starboard.

Also, now, when we turn on only the starboard key, the starboard Tach, speedometer, and both assist gauges come on as they should.

So, far, so good.

Now, we turn the starboard battery switch off and the port switch on 1, and again the port gauges are not on and the port engine will not crank. Turning the starboard battery switch to 1, makes the port engine crank.

Further reading of the manual we have we discovered the above paragraph. What this means to us is, The SmartCraft gauge system (which includes the key switches) can only be powered by one engine's battery system. And in this boat, that happens to be the starboard engine.

Now, I can live with this situation, but I'm kinda anal about things working correctly, and "logically". On this boat, everything else is independent on each engine. Seperate fuel systems that will not cross over, seperate battery systems, but...............apparently not seperate ignition key systems.

Are we overlooking something?

I am convenced our battery switch wiring is correct. All the voltages check out as they should at the battery switch. Switching batterys between the engines works as it should. The issue lies in the SmartCraft wiring harness, Either in the design, or in something we are unable to figure out.

Sure would appreciate any technical help from THT.
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Old 07-11-2012, 05:24 PM
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Nope...mine does the same thing....in fact 3 smartcraft boats that way....just wired to one motor....I'm just not that "anal".....both keys are on when I need everything....

Last edited by Glen E; 07-11-2012 at 05:36 PM.
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Old 07-11-2012, 05:38 PM
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Originally Posted by Glen E View Post
...I'm just not that "anal".....
I never thought I'd hear you say that.

Thanks for the re-assurance that somethings wrong and I can't do anything about it.
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Old 07-11-2012, 05:40 PM
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I dont think for me any thing is wrong. I did not say that you can't do anything about it, I just don't care to, or spend money as its not a big deal. I'm sure a good smartcraft tech can get everything to share......
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Old 07-11-2012, 07:40 PM
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Fshmn - what you described is... I believe the correct operating situation. And it is because there is only 1 shared CANbus network between twin or triple engines. And everyone seems to pick the Starboard Engine / Battery as the master to power it. So, when you turn on the Starboard key, that puts power to the CANbus and activates all of the gauges, neutral safety switch in the DTS control, etc and will allow the engines to start. I do not believe that Mercury supports a design to have the network powered at multiple points. So I believe this is kind of a Single Point of Failure. It would be nice if there was a work around, but I do not know of one. Of course, you can combine batteries if you are just out of power in a battery, but if you actually loose the CANBus wiring connection on your Starboard motor, it will cause you to not be able to start and run your Port motor. At least that is my understanding.
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Old 07-11-2012, 08:16 PM
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SaltyG, that seems to be the case. I have re-read the Wiring for SmartCraft Gauges and can't seem to interpret it any other way.

Glen E/SaltyG.: Prior to today, I had a single CAN Bus in my console. The result of having that wired that way was:

Either key turned on all gauges, however, the system key that was OFF, kept the corresponding Tach from displaying any info.

The Speedometer and it's displayed info worked if either key was on. Fuel, Oil, Tilt, Temp, etc.

With both engines running, initially, both voltages would be different. i.e. 13.8V and 14.1V.
After a short while, both voltages would read the same.

The Mercury Tech suggested we install a second CAN Bus with a harness connector between them. One engine went to one CAN Bus and then to the port Tach. The other engine went to the second CAN Bus and then to the starboard Tach and Speedometer.

The Tech thought that the voltage leaking between the two systems was a fault we should correct and felt the addition of the above parts would cure the voltage problem(?).

I don't know yet if this worked to isolate the voltages, but, it did seperate the gauge displays to match the key that was switched on. Port key on only illuminates port tach and assist gauges, Starboard key illuminates starboard tach and assist gauges and speedometer.

I can actually return the parts I installed today (~$120) and go back to the way it has been for a year, or keep the parts and eleminate the voltage problem(?).

I am unsure exactly what was happening with the voltage and is it worth the money to correct?

All along I thought I was going to correct what I felt was a battery switching problem, but now realize that what I have done is not going to correct that situation.

Any ideas on the voltage issue?
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Old 07-11-2012, 08:20 PM
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Originally Posted by SaltyG View Post
........ but if you actually loose the CANBus wiring connection on your Starboard motor, it will cause you to not be able to start and run your Port motor. At least that is my understanding.
SaltyG: That is the part that is concerning me. I have felt comfortable feeling that I had two "independent" engine systems and could come home on one engine no matter what the problem might be with one of them.

Now, I have a new anxiety. Perhaps I need a kicker.
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Old 07-12-2012, 05:47 AM
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Let us know what you find out. I wouldn't think you would want two separate busses and not sure why you have the voltage issue unless you have a battery switch set to both. It would be interesting if you ever talk to someone at Merc that has a solution for this. Thanks.
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Old 07-12-2012, 03:25 PM
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SaltyG, from what I have found out, everything we have discussed is what it is.
If you have a CAN Bus problem with the starboard engine, it's time to call Sea Tow.

Batteries are not an issue as they can be crossed either way. Starboard must have voltage or you might as well break out a Snickers.

Out of curiosity today, I thought I'd look for the plug at the motor end that you disconnect on the port engine and have connected on the Starboard engine. Good luck with finding it. I gave up.

I'm not sure there is a voltage issue, but I'm going to watch my meters a lot closer on Saturday and see if they zero sum out to the same volts while running. If so......... I think I'll just live with it. Too many other undone projects to finish on the boat.

Ok, so it is what it is, thanks to you guys for chimming in on the issue. We put everything back like it was 48 hours ago and returned the parts.

Engines are a lot more complicated nowdays than the old 5HP Elgin I grew up with.
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Old 07-29-2012, 10:11 AM
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Out of curiosity if you have a can bus harness on both engines, will you need to still disconnect power on one of the engines? I have 2 seperate harnesses going straight to the helm to a junction box. I don't want to hijack the tread so I won't get into my problems but just wondering about the CAN power.
Thanks!
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Old 07-29-2012, 08:35 PM
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fshon:
It's confusing but I believe I have what you have described as well.
Two harnesses going to one Junction Box at the helm.
Read my first post. The manual says you must disconnect one of the power supplies at the motor. Apparently, most chose to disconnect the port engine power.

Don't worry about hijacking the thread, I believe my situation is resolved as best it can be.

Feel free to toss out another problem.
Maybe it's one I have and don't know about.
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Old 07-30-2012, 11:29 AM
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Originally Posted by fshmn View Post
The manual says you must disconnect one of the power supplies at the motor. Apparently, most chose to disconnect the port engine power.
I saw that too, but that is (if I understand it correctly) if you have 2 harnesses from each engine going to a junction box near the back of the boat, then a single CAN harness going to the helm to another junction box, then to your electronics.
But for some reason I ran a CAN harness from each engine to the helm, to a junction box. I am using a Navman unit with a gateway to get my engine data. I have the port engine CAN power disconnected. To get the gauges to show up on the Navman i need to turn on the starboard engine first then the port. My problem is that when the engines are running in the water I'm not always getting smartcraft info, It's weird. I don't have a terminator on the junction box, which might be my problem, but doesn't say to use one in the gateway manual.
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