The little Yanmar engine in our J/109 is cursed with the basic panel that has no gauges other than RPM and just warning lights for other parameters.
While I have taken a bunch of precautions against overheating, which I have written about before, I really wanted to be able to read engine temperature because:
- It’s good to know that the engine has reached operating temperature before increasing the RPM to full cruise.
- Conversely, on short engine runs, like just leaving the wharf to put the sails up, it’s good to be sure the engine has reached operating temperature before shutting it down, even if it means motoring a little further.
- Monitoring engine temperature can warn us of impending problems like a damaged water pump or partially blocked strainer well ahead of the alarm going off.
- Conversely, persistently low engine temperature, which is also bad for the engine, can warn us of a thermostat that has stuck open.
There are various ways to add a conventional temperature gauge to an engine in the absence of another threaded port, including teeing it into the water heater heat exchanger circuit, but that would mean finding a home for the gauge on deck, and cutting a hole to accommodate it.
Here’s a better and easier way:
I’d discovered Yacht Devices, recently, and for the same basic reasons you list here… I wanted/needed to get more insight into what my engine is doing while I’m busy navigating. And, I think Yacht Devices is a *wonderful* business. They make things easy and relatively inexpensive, (you know, as far as marine electronics goes), for example, they offer many, if not all, their devices with standard NEMA 2K connections, or Raymarine STNG connections, which saves one the $40 US for the “converter” cable, if they have a Raymarine network on their boat.
I’ve gotten both the standard engine temp. sensor, and the exhaust system temp. probe, and altogether they were less expensive than the HDPE water lift muffler I had to replace because of a raw water cooling issue.
Hi Karl,
Good point on the ROI of doing things like this.
That probe will read a bit cooler than the true engine coolant temperature. It is taking in heat via conduction through the fitting, but is also losing heat via convection to the surrounding air. Its calibration will not take this into account. If the true coolant temperature is 74°C then this might read somewhere between 60°C and 70°C depending on exactly how it’s mounted and the temperature of the engine room ambient air.
As long as you make a note of what reading on the sensor corresponds to “fully warmed up, normal operation” and are just using it to see if you’ve hit or exceeded that mark, it’s fine. Just don’t expect absolute accuracy.
If you need a more accurate reading, you can wrap the sensor and the thing it’s monitoring in a bit of pipe insulation and tape. Then it’ll show close to the true temperature, but with a delay / lag.
(We see this issue all the time when doing thermal performance tests on new devices in the lab, when you have to tape dozens of sensors all over the thing and put it in the hi-temp chamber.)
Hi Matt,
Good point, although having shot around the engine with an IR gun I think it’s only under reading by 2C or less. Anyway, not really a problem in that what I’m really looking for is change from normal behaviour and/or the engine being warm enough to run hard, where accuracy is not critical. I did think about insulating it, but would need to find some high temp insulation. Definitely would be even better after doing that.
The insulation doesn’t need to be anything fancy… you want to create a small temperature gradient outside the sensor to get it closer to the measured surface temperature. A couple of wraps of silicon pipe repair tape would suffice to slow down the heat escaping from the sensor.
I too have incorporated yacht devices modules into my NEMA2000 bus and use it to display all kinds of info. I did purchase the engine gateway. It has worked well and provides a plethora of important parameters. I have started to experience glitches of late with the network leading to some of my displays not reporting data. I have a data logger, temp/humidity and the Yanmar engine gateway. I plan to systematically remove each device to determine if they are the problem. I have a fairly complex system and it could be another device on the network. With all this convenience comes some problems.
I love the engine gateway.
Hi Thomas,
Yes, NMEA 2000 networks can get flaky as they get more complex and unfortunately that’s fundamental to the architecture: https://www.morganscloud.com/2013/05/26/nmea-2000missing-the-obvious/
The first thing I would do is use this software to document and check the network: https://www.maretron.com/products/n2kbuilder-nmea-2000-network-design-software/
Mmm, I prefer the JET concept (just enough technology) and this sounds like TMT (too much technology). Electrics in a marine environment are bad enough without having too much of it to rely on.
In the two and a half years we’ve been cruising full time, the major conversation topic over coffee or sundowners with other yachties in anchorages is about fixing electrical and electronic devices, that we simply didn’t have (or need) not that long ago.
Electricians who sail are by far the most popular sailors in anchorages, rarely having to buy their own drinks and always with as much paid work as they want. Which tells me something.
Hi Paul,
Me too, and I love the JET acronym.
The key is a balance between function and overdoing it, and, at least for me, the benefit of knowing engine temperature comes out on the right side of the scale.
On the other hand it’s all too easy to go too far. More thoughts on that and how to avoid being driven crazy by TMT: https://www.morganscloud.com/2016/01/08/marine-electronics-system-recommendations/
And of course the right balance depends on the person involved. I’m an electronics tech by trade so find this stuff easier than many people will.
I can’t lay credit to the JET acronym, that belongs entirely to John Kretschmer, who’s been banging this drum for a while now.
But irrespective of that, the point is that most of us are not competent to fix electrical issues and yet we are having more electrical devices increasingly foisted on us with very little thought of how reliable it is or how we might do without it for even the three or four days it might take us to sail the 500 miles to somewhere that someone can fix it. If the fault relates to critical systems like steering, navigation or sail handling, then what? Hand steering for three or four days might as well be three or four months in terms of our ability to do it.
But we’re now well off the topic of a mere temperature sensor, which was the point of John’s article.
Foisted? I would say yes if you are buying a new or nearly new boat. The market certainly leans into unneeded tech. The boat builders would argue that the market expects the tech and they are only keeping up with demand. If your boat is of a certain age then the tech was a choice. As an installer of “tech” I find most of it unnecessary but it is what the market wants, I have talked many customers out of unnecessary complications only to find they have latter added the bells and whistles down the road. I think in general we like complexity despite how much sailors claim otherwise.
Hi Carl,
Sadly, I would agree with your analysis. And I have to admit that though I try to warn against overdoing it in most articles (like the one above), I do catch myself getting carried away.
A lot of people do like the complexity. Engineer types, in particular, tend to get bored easily if they don’t have something to putter with, upgrade, and fix.
That desire is not universal, though. I’m one of those engineer types, and I spend all day with cutting-edge equipment (think “laser that takes images of what’s happening inside the beam of a bigger laser at a quarter-million frames a second”)….. but when I go to the boat, I want to get away from that. I want a boat that is utterly reliable, and whose systems can be fixed with a screwdriver and a wire crimper – if I have to pull out a laptop, either underway or at the dock, then my recreation time is starting to look too much like my job and I’m going to get grumpy.
I use openplotter my boat which is a deep well of time and issues on its own but one of the first things i did was putting “1 wire” temp sensor all over the place. Cabin, computer enclosure, fridge, batteries, mixing elbow, alternator. No alarm yet but dumping that data to a DB to learn what’s normal for my setup. I’m still missing the engine gateway to match those to RPM but that’s a fall project
I’m a software engineer and work in operations managing large server farms so I’m looking at it through those goggles but I get a bit miffed when I see people acting on their boat’s systems without data to back it up.
For your example, the absolute reading on your engine temp isn’t really important. I doubt you’ll call the engine supplier complaining that your temp is 10c below specs. Knowing that the average temp at cruising revs is creeping up slowly for the last month, now that’s something you can do preventative maintenance on.
Granted, I’m not building an expedition boat but I dont believe that falls in the too complex category. Don’t ask that question to my S.O. though… Anyway, the boat still runs if openplotter is down, I’m just trying to predict ahead of time *when* the fridge and engine are going to go on strike. And that puts a damper on sail time, even on a lake.
Hi John,
As mentioned by others, more tech = more things that will fail. An obvious fact. Still, another obvious fact is that not all failures are big problems. If the systems are organised well, most failures on the boat are just inconveniences that don’t influence the core functions of the boat at all. The engine temp update you did here falls well into this non critical category, of course. It doesn’t influence the core operations of the boat at all. It’s just a useful extra.
Adding tech gets problematic when we put it into the “chain of command”, where a whole vital system won’t work if the added tech stops working. The LA lithium backup system is a good example of removing such a dependency. It removes the complexity from the chain of events. Of course we need other types of backups too, like another way to navigate reasonably well if the electronics fail, but that’s not what I mean. If we use electronics to make handling the boat more comfortable, I see nothing wrong. If the boat cannot be steered without electronics, say a “steer by wire” system, that’s a bad system. Maybe good in a car or a fighter airplane, but a catastrophy waiting to happen on a boat.
It’s pretty much always possible to have a very complex and modern functionality, if wanted, but still without the vulnerability it brings, because the complexity works side by side with the core systems. The advanced stuff might be bling or might be very useful, but the boat doesn’t depend on it. If we feel unhappy when the bling stops working, we’ll get extra jobs and stress on our trips, but it doesn’t influence our safety or mobility. Perhaps we can live by the KISS principle at the same time as we indulge?
Hi Stein,
I agree with that and like your “chain of command” a lot.
However I would add one caveat: too much complexity can add a lot of distraction, particularly when it fails, and so can add risk even when the failure itself does not affect the operation of the boat.
I do find that BLING failure makes my customers sad. Multi color LED cockpit lights are bling but I have seen thier failure frustrate and irritate boaters to where it ruined the weekend. People become very attached to the toys and when they can nolonger control the auto pilot from their watch they stop having fun because the toy is broken. Although I agree that John’s simple temp gauge hack is more additive than negative. It is a balance they we humans often fail. At least us first world materialistic types. (Note I am in this group too often) Do as I say not as I do…
On my little Yanmar there is an unused alarm circuit for water in the sail drive. I don’t have a sail drive. I added a simple exhaust temp alarm on the mixing elbow. If the Impeller goes the elbow will overheat very quickly. Much faster than the engine. This is of course a different function than engine temperature, but your solution made me think of this simple modification. It is also completely different from a pyrometer for monitoring engine load. It’s really an Impeller or sea water flow indicator without having to insert a sensor into the flow.
Hi Carl,
Good idea. I have an exhaust temp alarm too, and regard it as required equipment. (#6) https://www.morganscloud.com/2023/07/17/10-tips-to-save-your-engine-from-overheating/
Hi John,
A quick thought on your bullet about making sure you get up to operating temperature. If engines behave like theory says they should and like compressors actually do (we studied this), I think that bullet may need a caveat saying that it only applies if this is a regular use case.
Research has shown that by far the most engine wear on the critical parts where wear matters (rings, etc.) happens during the warm up period (SAE has a few papers on this, I have a recollection of the most relevant one claiming around 70% of ring wear in gas engines for an average car use case is prior to reaching operating temp but my memory may not be quite correct). So limiting number of cycles through this warm up cycle is obviously important. Also, limiting time in warmup is key. In general, slowly increasing load as engine temp comes up is good practice and trying to idle up to temp before applying a load is really bad practice just as immediately applying a high load after a cold start is bad practice.
If you are just motoring for a few minutes after a cold start, I think it is actually best to just shut down and go sailing rather than to keep motoring and waiting until you get up to temp. When you shut down, you immediately stop the wear. When you keep motoring, you keep wearing at a slowing reducing rate until you hit the steady state rate. The next cold start, the engine has no idea what happened during the last cycle so it starts at the high wear rate again but this start has no bearing on the start that we were worried about.
That assumes that these cold start and short run cycles are not the normal operating cycle for the engine. If you do a lot of them, then you can have a few problems like increasing water content in the oil, sludging, etc. There are some use cases like a boat in a slip with a very short motor to consistent breezes where these short runs are the norm. Then I think it would probably be best to shut down as soon as possible as more occasionally (every 3-4 weeks?), go out and intentionally motor hard for an hour plus do more frequent oil changes than the hour meter would suggest.
Eric
Hi Eric,
Great explanation, thank you. I did know that idling up to temperature, as we so often hear advocated for, was wrong, but did not know that it was better to shut down rather than run to temperature on a short run. I will change my practice to reflect that, particularly since I already do the occasional longer hard run to dry the oil out. I will also make a Tip out of your comment since it’s really good to know and counterintuitive.
Hi John,
Glad it was useful. I looked quickly and the number I remembered is actually from Gumbleton’s “Piston Ring and Cylinder Wear Measurements Illustrate the Potential and Limitations of the Radioactive Technique” published in 1961. Obviously dated and there have been some significant improvements in engine materials and oils since then but at least still illustrative. What he found was that in a 2 hour test run from cold (room temp, not real cold), 75% of the wear occurred in the first 6 minutes of operation. The way they run these tests is to dope the rings with a radioactive isotope then they can measure it in the oil that has just gone through the cylinder and get accurate measurements of wear volume. A more modern look at the same issue is SAE 2006-01-3413 which uses more modern oils and engines but finds a similar correlation and several other papers touch on it too. The actual papers have wear graphs that quite graphically show how well wear correlates with coolant and engine oil temps.
You can go down quite a rabbit hole on this one. For example, early on they thought the main source of wear was combustion by-products causing corrosion on cold engines but now the list of reasons is much longer. One thing that will confuse a lot of people is that most of the wear occurs near TDC so you see the cross-hatching gone there first. Not only is this where the highest pressures occur (cylinder pressure gets behind the ring and pushes it out against the cylinder wall), it is also where the ring is going slowest which is bad from an oil film perspective. I am out of date on this stuff and was never close to being an expert. If someone spent the time reading all the research, they could go way beyond what I have written here.
To me, this all suggests that the biggest thing we can do is to not do unnecessary cold starts. I know people who just start the engine and run it for a few minutes every few days to “circulate the oil” and I suspect that this is quite detrimental (oil starvation on startup is a real thing but this isn’t solving it). Similarly, people sometimes have setups where the engine has to run for just a moment for a hydraulic or high power electric device to run and doing this once a day can add a ton of starts. I don’t know if there is data on this but I would hypothesize that the actual ambient temperature for the start matters although this is a lot harder to deal with on boats than cars. Of course, all this probably doesn’t matter for an awful lot of people as they don’t use the engine enough for it to matter and the death will be corrosion or lack of parts availability but for people who do use it regularly but not constantly where it is always at temp, it can be a big deal.
Eric
Hi Eric,
I’m very far from an engine specialist, but I believe I have put to use one solution that might help against cold start wear on some engines. I have two old Yanmar 3GM-30 engines. They have a decompression lever on each cylinder.
I’ve connected them with a rod. A cable from the steering position is connected to the rod. Before a start, I always use this to run the motors about 10-15 seconds with no compression, while holding in the stop button, to not pump diesel into the chamber. I don’t really know, of course, but I imagine this spreads the oil around in the engine while the loads are minimal.
This is also a way to definitively stop a runaway engine, if that was to happen. It’s also a backup if the stop button doesn’t work for normal stops. I assume it’s not possible to do this on engines without this lever originally present. However, many engines have this, while I’ve never seen one rigged for practical use. A missed opportunity?
Hi Stein,
Cranking with the compression released definitely helps with oil starvation during startup but I have honestly not seen much data to suggest this is a big deal (I would happily look at it if someone has it). However, I don’t think it is going to help with the wear we are discussing which takes place over several minutes. This wear is highly tied to temperature. There is also the danger of people cranking too long and filling their exhaust with water, this can be overdone.
The only practical thing I can think of would be for people with shore power or big batteries and plenty of charging, they could run a block heater and an oil pan heater (oil temp seems to be quite important) for an hour before starting or something. I don’t think there is an equivalent of parking in the sun like I do with land based machines when it is cold. Personally, I would not go to the trouble of adding heaters but we don’t have a use case that is a lot of starts and I think this engine will likely age out before wearing out.
One other thought is that while compression releases are quite simple, they are not a good candidate for a DIY job as it would be quite easy to get it wrong and have pistons hitting valves. I would rather plumb in an oil priming pump but again, I don’t find it worth it for myself. Certainly if you have the release already and don’t crank too long, I think it can only be good to do what you are doing.
Eric
Hi Eric,
I find this really interesting, thank you for taking the time. A bit geeky, I know, but the thing that really gets me going on this kind of thing is that it’s just another of the many times I have seen common practice around boats turn out to be not just wrong, but destructive. Trickle charging batteries over the winter comes to mind. I’m working distilling this in a Tip, so thanks again.