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      A Few Simple Rules   05/22/2017

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steele

motor overheat protection

18 posts in this topic

This years winter project is to service my engine's cooling system. It has been 10yrs since the hoses were replaced, so it is time. As near as I can figure out the only thing to really kill a simple diesel like mine is overheating, other things will stop it running but are less likely to ruin the motor. It has a low oil pressure and overheat alarm, but the one time I was on a boat that had an impeller fail the engine was cooked even though we shut down as soon as the alarm went off (it was a gass outboard). I was wondering about added layers of protection and came across 2 simple options,

 

The first is a flow sensor that goes on the intake side of the system, at first glance it looks to be a good idea, but because it is an inline part will add a weak link,

post-27422-0-99687200-1353517080_thumb.jpg

 

The second is an exaust temp sensor, which does not add any parts to fail in the circuit, but might be too "after the fact" to help,

post-27422-0-90467800-1353517268_thumb.jpg

 

I was wondering if anyone has experience with these types of devices, or perhaps knows of something better. I do service the water pump, clean the strainer and change the impeller on a regular basis.

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All you really need is an alarm. Google Borel Alarm. A diesel has pretty high exhaust gas temperature if the waterflow stops, and will set off the alarm before anything melts.

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I am a HUGE fan of inline sensors for water flow. this will give you the first warning before any over heat. if you go the groco route like this one listed here; http://www.groco.net/SVC-MAN-07/Sec5/PDF/SSA-1G.pdf it will record a baseline and when you start to lose 20% of that baseline flow it lets you know. So even when you start to get restriction in the line just from growth it will let you know and you can be preventative in nature. Plus you get a nice visual gauge as well.

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I like the exhaust monitor, and was just reading today about the intro of that NASA / clipper unit. Sounds like a good solution. The one thing I don't like is that the display / alarm is not waterproof, so has to be stashed somewhere watertight - which pretty much means out of my sight lines when I'm at the helm. Not a show stopper maybe, but if an alarm goes off down below and I have to go figure out what is going on - there will be a delay.

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section of rubber hose in the wet exhaust

 

flow stops = smelly smoke

 

simple

 

fail safe

 

cheap

 

some sensors rely on electrics

 

 

engine gets shut down VERY quickly !

 

 

Every Time ....

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I installed thein line flow sensor after I had a yanmar 3ym30 overheat. The problem was the alarm went off after damage was done to the wiring harness. It should have alerted me before damage was done. (I think I caught a plastic bag on the sail drive.) Engine ran fine even without the harness. No tack and I had to watch it like a hawk until i got the new harness installed.

 

Flow sensor worked fine for a season but during commissioning this year no water would go through. Ending up taking them out of the system and things stated working fine. On closer inspection when you look at the device it really restricts the flow.

 

Right now I am back to having nothing. My ideal system would be a simple thermostat that is set to ring a loud bell.

 

Bottom line I DON'T RECOMMEND the flow sensor. I had the exact same item you have pictured.

 

This years winter project is to service my engine's cooling system. It has been 10yrs since the hoses were replaced, so it is time. As near as I can figure out the only thing to really kill a simple diesel like mine is overheating, other things will stop it running but are less likely to ruin the motor. It has a low oil pressure and overheat alarm, but the one time I was on a boat that had an impeller fail the engine was cooked even though we shut down as soon as the alarm went off (it was a gass outboard). I was wondering about added layers of protection and came across 2 simple options,

 

The first is a flow sensor that goes on the intake side of the system, at first glance it looks to be a good idea, but because it is an inline part will add a weak link,

post-27422-0-99687200-1353517080_thumb.jpg

 

The second is an exaust temp sensor, which does not add any parts to fail in the circuit, but might be too "after the fact" to help,

post-27422-0-90467800-1353517268_thumb.jpg

 

I was wondering if anyone has experience with these types of devices, or perhaps knows of something better. I do service the water pump, clean the strainer and change the impeller on a regular basis.

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I did the burning rubber hose gig on a charter boat last January in the BVIs, decided I don't want to do that again. I installed the Borel alarm on my own boat. Cheap, simple, nothing else in the water flow to clog.

 

http://www.borelmfg.com/products_alarm.htm

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many sensors in the water flow will not work if there is no coolant

 

 

a head bolt temperature sensor will cover that possibility

 

 

I still like the terrifying rubber hose section in the wet exhaust

 

why do you think the charter boat had it ?

 

 

 

P. S.

 

another is to fit a small bypass hose from the top of the wet elbow { syphon breaker },outlet visible to the helm, but can be missed

 

also done with jet skis and outboards, directed upwards

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many sensors in the water flow will not work if there is no coolant

 

 

a head bolt temperature sensor will cover that possibility

 

 

I still like the terrifying rubber hose section in the wet exhaust

 

why do you think the charter boat had it ?

 

 

 

P. S.

 

another is to fit a small bypass hose from the top of the wet elbow { syphon breaker },outlet visible to the helm, but can be missed

 

also done with jet skis and outboards, directed upwards

 

The mixer elbow alarm is better than a block mounted sensor. The volume of antifreeze in the closed system will keep the engine cool while the hot exhaust melts your hose or waterlift. The engine overheat alarm is on the engine, so that is why it goes off too late.

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I have run diesels hotter than they are supposed to be run for long periods of time. We ran a chrysler/nissan 4 cyl. at 220 f (fresh water temp) for days. I think a lot of current raw water motors are thermostated at about 140 f, maybe fresh water engines higher, 180-200 f? An audible alarm at 10-15f over normal should alert you before failure.

 

That chrysler/nissan 4cyl running hot was 1974. Commissioning was botched on a "New Boat". Motor still ran good when we last pulled the boat out of the water in 2008, thousands of running hours later.

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Thanks for the information, it looks like a wet exaust overheat sensor is the way to go, not as quick to alarm as a flow sensor, but simpler and more likely to save the day than the alarm on the engine itself.

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This years winter project is to service my engine's cooling system. It has been 10yrs since the hoses were replaced, so it is time. As near as I can figure out the only thing to really kill a simple diesel like mine is overheating, other things will stop it running but are less likely to ruin the motor. It has a low oil pressure and overheat alarm, but the one time I was on a boat that had an impeller fail the engine was cooked even though we shut down as soon as the alarm went off (it was a gass outboard). I was wondering about added layers of protection and came across 2 simple options,

 

The first is a flow sensor that goes on the intake side of the system, at first glance it looks to be a good idea, but because it is an inline part will add a weak link,

post-27422-0-99687200-1353517080_thumb.jpg

 

The second is an exaust temp sensor, which does not add any parts to fail in the circuit, but might be too "after the fact" to help,

post-27422-0-90467800-1353517268_thumb.jpg

 

I was wondering if anyone has experience with these types of devices, or perhaps knows of something better. I do service the water pump, clean the strainer and change the impeller on a regular basis.

I think that on an outboard the cooling water is used to cool the exhaust right at the engine block, 2 cycle exhaust, uncooled, can probably heat an outboard engine very rapidly. A friend indicated frying an outboard engine with a bad impeller in a minute and I was amazed.

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everytime I have lost raw water I was able to imediatly detect the issue from the sound of the exhaust, however recognizing there are times this may not work (charging while sailing, storm conditions etc) I recently installed the Borel alarm. It is simple enough and looks like it should work, but no way to test it without potentially damaging the exhaust.

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The mixer elbow alarm is better than a block mounted sensor. The volume of antifreeze in the closed system will keep the engine cool while the hot exhaust melts your hose or waterlift. The engine overheat alarm is on the engine, so that is why it goes off too late.

 

Exactly. We had black smoke down below, but the engine temp was still normal. I imagine we pretty well cooked the exhaust hose downstream of the mixer, fortunately I didn't have to fix it.

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The outboard we cooked was a 3 cyl 2 cycle, it burned the center cylinder within a few seconds of the alarm, most likely it was well on it's way out before the alarm sounded. I may have bad luck with this type of thing, I have been associated with 2 other similar events. One was a freind's brand new V8 gas ski boat, when the alarm sounded he shut down and raised the engine cover to discover one cyl bank was glowing red. Note sure what the cause was, it was still under warranty and we were all hoping it was an internal issue, not a blocked intake. The other case was running into a marine mechanic I know who was working on a dockmates boat. They were motoring and noticed a slight change in pitch from the motor and shut down immediatly. The mechanic proudly showed me the cause he had found, a fish perfectly sized to fit in the intake hose. The boat had no strainer and the little guy got sucked in, a one in a million thing.

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The outboard we cooked was a 3 cyl 2 cycle, it burned the center cylinder within a few seconds of the alarm, most likely it was well on it's way out before the alarm sounded. I may have bad luck with this type of thing, I have been associated with 2 other similar events. One was a freind's brand new V8 gas ski boat, when the alarm sounded he shut down and raised the engine cover to discover one cyl bank was glowing red. Note sure what the cause was, it was still under warranty and we were all hoping it was an internal issue, not a blocked intake. The other case was running into a marine mechanic I know who was working on a dockmates boat. They were motoring and noticed a slight change in pitch from the motor and shut down immediatly. The mechanic proudly showed me the cause he had found, a fish perfectly sized to fit in the intake hose. The boat had no strainer and the little guy got sucked in, a one in a million thing.

 

I have had two overheat events due to fish in the intake. I wish I was as lucky with the lottery.

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One in a Million ? Two in a Million? Hope the front doesn't fall off.....

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Impellars don't generly fail while running, If water starts flowing when you start the engine you are almost guarenteed that it will keep running.

 

Make the habbit of cheaking water flow out the exaust EVERY time you start the donk.

 

That and the over temp alarm the basic yanmars have will catch 99% of over heating alarms.

 

A freind of mine has forgot to open his sea-cock at least a couple of times and the yanmar over temp alarm have saved him from isues every time, I don't know why he doesn't just check exaust water every start?

 

Note, both engines are salt water cooled.

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