Raw water temperature or pressure?

[HeadedToTexas]

Rather than roll the dice that my 2007 Cummins QSB is compatible with Mercury's SmartCraft Connect, I have decided to replace the old DieselView unit with some gauges that simplify monitoring. The entire suite of variables will still be available through the SC1000 digital display including both raw water temperature and water pressure. It seems like water temperature is the more common of the two variables to monitor, but water pressure would lead temperature as an indicator of problems, true? Whether it's a clogging strainer, failing impeller, or burst coolant hose, pressure would fall before temperature would climb. So does that make water pressure a better indicator of impending problems?

Or it could be that pressure is a better indicator of critical failure, but temperature is a better indicator of problems that indicate a need for maintenance. I may be a data guy, but I'm not a diesel mechanic. What would you guys do if you could only have one of those two gauges?

 

[rslifkin]

On the raw water side I'd either want to measure pressure or exhaust elbow temperature. Those will be the 2 fastest indications of low or no water flow (pressure will also vary a good bit with RPM). Temperature elsewhere in the raw water circuit is likely not a very useful measure.

 

[Comodave]

We put Borel Manufacturing alarm system on several boats and they worked well and are simple to install. The exhaust water sensor is like a big tie wrap that goes on right behind the exhaust water injection l. It will sense lost water in a couple of seconds. You can also put a Water In Fuel sensor in the Racor. And a high water alarm. Much easier than messaging with all separate sensors.

 

[HeadedToTexas]

I like the Borel system and will likely have one someday. In this case, there are no new sensors as these are all variables the Cummins QSB is already measuring. I am just deciding which to have dedicated gauges to display. They look like analog gauges, but they display digital data from the SmartCraft network.

 

[Bmarler]

It would depend on where the sensors are located. If you measure temp just before the elbow it would be a good indicator of issues. Once you have a base line temperature you can monitor for change. I do this with my exhaust temperature and it lets me know if the strainer or impeller needs attention.
Measuring incoming raw water temp would not be as useful.
I also agree that pressure would be good to have. You might see slow changes over time as things wear or clog.
Differential pressure across the pump would be even better.

 

[O C Diver]

First, are the audible alarms still going to be available if you remove the display?

What pressure value is displayed under normal operation? I'm guessing the pressure scale on the gauge is too large to be meaningful.

Personally, I'd rather have a raw water temperature gauge between the heat exchanger and the exhaust elbow.

Ted

 

[HeadedToTexas]

The DieselView display panel doesn't really get removed, just removed from the dash. It has to remain as it is part of the SmartCraft brain. Getting rid of it altogether means pretty big surgery and going back to the native J1939 spoken by the engine. Thought about it, but it's too big a job when the SmartCraft stuff still works reliably.

I am not certain where the QSB gets its water temperature measurement, but I'll look into it.

 

[DDW]

The Smartcraft Connect does in fact work on the QSB, I had one on my 2006 QSB for awhile. There are others that work as well, I am currently using the Yacht Devices product, which forwards more of the engine data to the N2K bus than the Mercruiser product. That makes all the engine data available on the MFD and other display heads, and the normal alarms show up there as well. You will still need to look at the Mercruiser display for specific alarm data with no N2K equivalent (such as the low lift pump pressure when my lift pump failed in Alaska).

My 2006 engine does not have a raw water temp or pressure sensor, only the coolant circuit. Any response from the raw water circuit doesn't have to be instant, as a failure there takes at least a short delay to cause overheating in the engine coolant. Of more immediate concern may be overheating the muffler, if raw water were to suddenly quit flowing, so exhaust temp might be the best coverage.

 

[HeadedToTexas]

The Smartcraft Connect does in fact work on the QSB, I had one on my 2006 QSB for awhile. There are others that work as well, I am currently using the Yacht Devices product, which forwards more of the engine data to the N2K bus than the Mercruiser product.

Very interesting. Despite detailed information on my engine, neither Mercury nor Cummins could tell me if the SmartCraft Connect would work. They said "some do and some don't; you just have to try it." Expensive experiment.

At this point, I have committed to and am happy about dedicated gauges in place of screens. Still, there is plenty of data that won't have a dedicated gauge. The Yacht Devices is about 40% the cost of the SmartCraft Connect. Where does it connect to the engine network?

 

[DDW]

Same place the Smartcraft does (you will probably need the Yacht Devices Smartcraft 10 pin adapter), usually there are multiple Smartcraft connections (there were in my boat), sometimes you need a spitter (I think they call in a Mux). It isn't expensive and I happen to have one left over because I was told I'd need it and don't (if you get to that point). You can find the real Smartcraft one on eBay much cheaper than from the dealer, but "you takes your chances" on eBay. The Yacht Devices is a bit more configurable than the Smartcraft (which is what it is), that means you may have to configure it (a text file loaded onto a microSD card), their tech support is good, also I could send you the file I use. But it will probably work fine out of the box.

The YD comes in two versions, one that plugs directly into a Raymarine backbone, and the other using more industry standard N2K connections. On my boat, I have configured a Raymarine i70s display head to show all of the interesting engine data, with the less interesting available on other pages. I pretty much ignore the Smartcraft display (it is dim and the menu structure obscure) but as I said in the case of an engine control fault it will display more info that will not translate to N2K. Critical alarms will light up on the MFD making themselves very obvious!