I'm adding extra engine temperature alarms

[03RLXi]

After this recent episode where it seems a brand new impeller wasn't immediately pumping properly (#) I've decided to add a https://engineguard.com.au/ dual sensor engine temperature alarm. Will put one sensor on the impeller housing and the other somewhere on cylinder head. Each has programmable alarm set points so I can have first sensor a few degrees about lake temperature and the second a few degrees above normal engine temperature.  I’ll update once I've installed and used it.

My thinking is it’ll be better than only having the original ECM alarm and the separate water temperature gauge, both of which need water to operate accurately. Plus these sensors are not water based. They're direct contact on metal and it won't take long for the impeller housing to warm up, and/or for the engine cylinder head to heat up. Both will be alarmed. If I to really belts and braces it I could add a water pressure or flow sensor after the impeller pump, but I think that'd be OTT and more likely to cause false alarms than the benefit it'd provide over the 3 alarms and 1 gauge I'll have. 

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# I fitted a new impeller and because it was first start of the season I had engine cover open to check for any dewinterising leaks. None but I touched the impeller housing after a minute or so and it was warm. Not hot but warmer than skin temperature. Immediately thought oh no impeller is burning up. Stopped engine and the moment I loosened the housing cover screws I heard gurgle as air entered and water drained into lake. So there was water being sucked in, but seemingly not enough. Removed cover, impeller ok, there was water in housing, refitted cover and restart. Noticed exhaust manifolds warmer than normal on top and rear. Impeller housing was warming up again. But after about one minute the impeller housing goes cold, exhausts go cold. Engine idling and temp slowly rises over next and stabilises at 165ish. Trial run on lake and all ok. Was a bit weird!

I've got to say I have never bothered putting hand on impeller housing before with this boat or prior RLX. Maybe it's been occurring in past but I just never knew!  I always have boat in lake on trailer when start it. Don't even own a fake a lake. They sound like high risk things to me!

[Drago]

I always check the impeller housing on spring start. When you're attaching the hoses back up you might also want to prime the system 

[BraceMaker]

I've always thought they should have something like hot tubs these flow switches cut the electric power to the heating elements to avoid damage in the event that there isn't enough flow that or some sort of pressure sensor in the hose between the raw water pump and the thermostat housing would be the canary in the coal mine giving you advance warning before the engine got hot instead of after the engine already was above temp.

 

[03RLXi]

Copied form another site "Indmar Raptor 6.2 engines achieved a way for the ECM to send an alarm if the water flow was not adequate.  The 2015-2016 models used an inline raw water flow sensor, similar to a speedometer paddlewheel sensor.  The 2017 and newer models used exhaust "skin" surface temperature sensors on the exhaust outlet tubes.  Mercruiser used a pressure sensor in the raw water system since the early 2000s."

Effectively I'm adding skin sensors but on the impeller housing and somewhere on the engine

[jpwhit]

The best place to monitor is the temperature of the rubber hose coming off the exhaust manifold(s). That's where you'll see the earliest rise in temp if there isn't much raw water flowing. 

[jpwhit]

You can remove the serpentine belt to test your setup. 

[DW]

Another tell tale is to grab the outlet hose from the raw water pump, you can feel the pressure (it tends to pulse along with being firmer) and temperature (cold) readily.  

[chrislandy]

I've been looking at SM022D Dual sensor, exhaust / engine temperature monitor (siliconmarine.com)for mine, it uses a thermocouple inserted into the exhaust flow so if the water mix drops off then it's almost instant rather than waiting for the manifold to heat up

[03RLXi]

10 hours ago, chrislandy said:

I've been looking at SM022D Dual sensor, exhaust / engine temperature monitor (siliconmarine.com)for mine, it uses a thermocouple inserted into the exhaust flow so if the water mix drops off then it's almost instant rather than waiting for the manifold to heat up

Interesting sensor.

My plan when it arrives is one sensor bolted to the impeller housing and other to somewhere on a cylinder head, although base don some comments here may in time I might move the impeller housing sensor to the hose clamp band on exhaust.   

[chrislandy]

@03RLXi pre my current boat, I was developing a small digital dash for my old 96 prostar with a separate sensor array to the main gauges i.e. completely independent. It had a oil pressure, oil temp, water temp, rpm and a raw water flow meter, plus rolling log so if something ever happened I'd have a log of some critical info. They key was using decent 3 wire sensors and using a 0-5v scale

Unfortunately (or fortunately) I sold the boat on and got my newer prostar before I'd finished it. I might still resurrect it but just use water flow and exhaust thermocouples like the above - but for £130 ~ $150 it's probably not worth my trouble and I'll probably end up just buying that other one.

[101driver]

I have added audio warning on my temp and oil pressure circuits. I picked up some weed a few years ago and it restricted the flow through the strainer pot. Engine was Ok because there was enough flow but the temperature started to climb on load in the course but was ok at the ends. As I don't usually have a spotter my attention is split between watching skier/ driving straight and speed check when in the course, not checking all of the gauges I only do that at the ends, so I did not pick up the temp rise. The audio sounders were pence to buy and just let me know to check. Dead easy fit.

[03RLXi]

The alarm hasn't arrived yet! Still somewhere between Australia and New Zealand. So much for air mail during Christmas rush 😞

I tried another start on ramp and housing began to warm up within 10 seconds. Had a really close look and then removed impeller. It looks like new. I lubed the housing a lot with dish soap and reinstalled. It seemed to be 1-2mm further in.  Within 3 or 4 seconds of starting there were bubbles in the lake. Housing cold and after few minutes idle reached steady 170 ish. Had done another cold start and up to normal temp cycle. All good. I think the impeller may not have been fully seated and hence was bleeding pressure a little on rear edge so still moving a tiny bit of water but not enough. So sorted completely, I think.   I still fit the alarm once it arrives.

[DW]

Good to hear although surprised it assembled with the impeller not properly seated.

[03RLXi]

5 hours ago, DW said:

Good to hear although surprised it assembled with the impeller not properly seated.

The impeller rubber pokes out in front of the brass hub so guess there's enough flexi that it allowed the cover to go on easy and still sit flat. I assume proper fit has it touching both back of housing and the cover quite tightly

[03RLXi]

I’ve fitted the https://engineguard.com.au/ dual sensor engine temperature alarm. The sensors are like an electrical lug so can easily bolt them anywhere.

I mounted first sensor to the cooling water impeller housing using existing cover screw.

I would have fitted the second sensor into a spare cylinder head thread, but I don't have a suitable bolt, so I mounted it via the existing transmission heat exchanger bolt.
I mounted the display down near my right knee - it's clearly visible but not obtrusive and easy to reach.

To set it up, I ran the engine normally around lake for approx 10 minutes and then pressed buttons to recall the peak temperatures and set the audible alarm parameters slightly above that. It showed that the normal temperature for the impeller housing was 22°C (lake water temperature) and the cylinder head was at 72°C. Initially, I set alarm thresholds to 30°C and 75°C.
 

It works great and has immediately proven useful. During our three-week Christmas holiday break, it never operated then one day on the first start of the day the pump didn't prime. The housing began to heat up, and the alarm went off. A quick blip of throttle primed the pump. Without the alarm, it could have resulted in a failed impeller and possible engine damage, burnt exhaust hoses, etc.
 

There is one minor glitch though. When the engine is turned off for several minutes, heat soak warms up the impeller housing to 40-50°C, and of course, it alarms on engine restart. It's not a major glitch though since a simple press of 'SET' button mutes the alarm for 30 seconds. The temperature falls to 22-25°C within 10 seconds or so, indicating that the cooling pump has primed and all is good. I'm really liking the peace of mind it provides by giving almost immediate feedback on cooling water flow.

The instructions mentioned that on boats to install a sensor near the outlet of water-cooled exhaust. Personally, I think having it on the impeller housing at the beginning of the cooling system is better than at the outlet, but maybe someday I'll move the cylinder head sensor to exhaust outlet so that both my inlet and outlet are monitored.