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Old 07-30-2016, 08:55 AM   #1
SKS
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High temperature alarm

Hello all,
New to forum. I've joined this site and others to learn and appreciate the fact that you're willing to take time to help.
Just got a 34' Mainship w/ Cummins 6BT 210 hp diesel ( my first diesel and first larger boat).
I'm trying to get info. about how to change my two high temp. alarms.
I've got VDO gauges, one engine/two stations, and the alarms seem to be on circuit boards connected to the gauges.
The alarms buzz at 190 F which I believe is too low. 200/ 205 F would be better.
Something simple and inexpensive (yea right) as this may not be permanent.
There is only one sender.
Another (preferred) option whould be adding a mute feature to what I already have since I don't expect to see 190 F very often anyway.
I would really appreciate your thoughts.
Thank you.
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Old 07-30-2016, 08:59 AM   #2
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High temperature alarm

If they are buzzing at 190 I would look into your cooling system before changing out the alarms.

Maybe run some Barnacle Buster through the the system. Many have done that here and had good results. Search for a thread by Flywright-- he details how to do it. It's not hard-- I did it on my boat with good results.

Good luck!


Here's the thread

Barnacle Buster-Magic Elixir Barnacle Buster-Magic Elixir
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Old 07-30-2016, 09:12 AM   #3
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Why are the alarms going off? IMO 190 is a little hight for normak operation. Are you running WOT? Under what conditions does it alarm?
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Old 07-30-2016, 09:15 AM   #4
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Thanks Cardude,
I'll check it out. Can't hurt to use Barnicle Buster.
I also plan on removing and cleaning the main heat exchanger. I've already changed the impeller. Water flow seems good out of the heat exchanger now but I don't know what it is supposed to look like as the boat is new to me. It runs at about 185-187 degrees
@ 2200 rpm in 85 degrees Chesapeake Bay bath water. Boat was in cooler salt water in Rhode Island for past ten years and ran about 183 degrees. Another step or two and the cooling is like new.
Thanks again.
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Old 07-30-2016, 09:30 AM   #5
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Hi Bayview,
Cummins says 181-203 normal range.
Plan on 1800-2200rpm as my usual range. WOT is 2600rpm. Alarm sounds as get to about 2400 rpm.
I'm pretty confident in the cooling system but will tweek it to be 100%. 34 hour trip from Rhode Island went great a temp was steady at 185. Warmer operating water seems to mean slightly warmer engine temp but well within range, just closer to alarm point. If I could silence as opposed to change alarm I at least it keep my margin but gain "silence" as I evaluate things.
Any thoughts?
Thank you for your time.
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Old 07-30-2016, 10:20 AM   #6
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Assuming that the alarm is OEM and on the boat when you got it then we can assume that the alarm was not going off with the previous owner. What changed? Do you run harder? Do you reach rated WOT?

Might be worth checking temp with an IR gun to verify the gauge.

Do you have a transmission cooler? Why are you so confidant about the cooling system?
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Old 07-30-2016, 10:24 AM   #7
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Quote:
Originally Posted by SKS;
Another (preferred) option would be adding a mute feature
Quote:
Originally Posted by SKS;
If I could silence as opposed to change alarm
Just.
Don't.
Go there.
OK?

There is nothing more permanent than a temporary repair.
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Old 07-30-2016, 10:51 AM   #8
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Did you burp the cooling system as described in the manual after changing coolant?
Is the high temp steady or does it move up and down while running at the same load?
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Old 07-30-2016, 10:55 AM   #9
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Great engine. Check on the BoatDiesel site, but I'm pretty sure that if your raw-water side is all clean & good, the recommendation there would be to swap out your stock 180F thermostats for 160's...they'll open a little earlier and likely solve the alarm issue.


And I totally agree with Hawgwash at post #7...VERY bad idea to mute/silence the alarm
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Old 07-30-2016, 12:01 PM   #10
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Bayview, Hawgwash, Aquabelle,

Thank you guys. This is great stuff.

...What changed? Not much. Previous owner saw 183 F he usually ran no harder than 2200 RPM in colder saltwater in Rhode Island. Now I'm seeing 185 to 187 at 2200 RPM running in Chesapeake Bay bathwater which is at least 20 warmer than Narragansett Bay, Is that reasonable in your collective opinion? As a test I goosed it to 2400 RPM and the temperature climb to slightly above 190 F and alarmed at 190 F.
Engine reached rated 2600rpm during sea trial Mid May, colder water more efficient cooling is what I am thinking. Thoughts on this?
Temps have been confirmed with IR Gun by surveyor and myself just last week and are within a degree or two of both helm gauges.
I am hesitant, for now, to change stat to 160 F per Boatdiesel as I'm right in the middle of the range and am not planning on running engine hard. Probably 1800-2200 RPM.
There is a transmission cooler. I checked the inlet an screen, it's clear. ASIDE: transmission was rebuilt after sea trial due to metal and water in oil sample.

My confidence in cooling system is just a confidence in water flow as observed by removing heat exchanger outlet hose before it enters exhaust elbow and running the engine for about ten seconds. Good flow observed.

...burp system? Have not changed coolant. Plan on cleaning heat exchanger soon. But that may or may not be part of the problem but it is probably due.

Temps are steady and dropped to below 190 F again after reducing rpm.

AGAIN: if I can believe the two gauges plus the IR Gun I am not running warm, I am right in the middle of the Cummins recommended range. the issue is an alarm that goes off a bit prematurely in my opinion.

Hey I'm here to learn. Maybe it's not premature at all and is at 190 F to alert operator early. What do you guys say?

...Don't go there. Thank you, I hear you loud and clear!
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Old 07-30-2016, 12:43 PM   #11
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Some observations:

190 degrees is not particularly hot, and as you point out Cummins says normal is 181-203, right smack in the middle of your alarm point. So don't change the thermostat. Warmer running is more efficient, up to a point ;-) and for all you know the existing thermostat is already fully open at 190, so changing to a lower temp won't help.

So I suspect that the alarm is set too low. I am a little, well a lot surprised that there is only one sensor for two temp gauges and an alarm. Typically alarms have their own sensor switch that closes at the set point. Perhaps Ski can help out on this as he knows Cummins and has one himself.

If you can find a dedicated alarm sensor then I will bet it is bad. If Cummins (or VDO actually) really built that engine with one analog sensor for both temp readout and alarm, then perhaps it can be adjusted, either with a pot or jumper. VDO makes temp switches with set points from 150-210 in 10 degree increments for separate alarms, so I will bet that circuit board has a way to change the set point. Maybe you should talk to someone knowledgeable at VDO.

In any case, once you get the coolant alarm fixed, consider adding a raw water alarm. There are two basic types: a low flow alarm- Aqualarm makes one and a high exhaust temp after the mixer alarm- Borel makes one. I like the Borel alarm- simple to install and not much to go wrong, unlike the flow sensor on the Aqualarm.

Lack of raw water has ruined more marine engines than lack of coolant ever did.

David
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Old 07-30-2016, 01:15 PM   #12
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Temps sound normal. Alarm going off at 190 is not. Alarm comes from the little pcb that monitors gauge signal.

Best thing is to remove the pcb and throw it in the water. It will be more reliable afterward.

Then put a dedicated temp alarm switch in the following locations: 1. front right of cyl head, should be an extra 1/2" port there for a switch. 2. Exhaust manifold top rear or turbo top. this gets hot if belt breaks or you lose coolant. 3. Exhaust mixer. This gets hot if you lose sea water.

2 and 3 can be snap disc switches.

Also install a 10# oil pressure switch on spare tap on oil gallery.

Boatdiesel has some good writeups on exactly this. Bill D??? burned up a b370 and then decided to make a proper alarm system.

You now have four alarm switches. Tie all together and put buzzer in overhead of pilot house. This works for both upper and lower helm. Lower it is right near your head, at upper it will buzz your feet.

I have the above alarm system on my C450, works perfect.

You can put a silence switch on, but this is risky. People forget things. I put a silence sw on mine. I have forgotten it. Lucky so far, no harm.
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Old 07-30-2016, 01:17 PM   #13
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Hi David,
Thank you.
I'll have to trace the wires to find our more. The sender has a black and a tan wire. Not sure what the black wire does. I don't think it's a ground as I believe the sender is grounded by screwing into the engine block. From what I see the tan wire runs from the one sender on the front, top of engine to the lower helm gauge onto a terminal and continues to upper helm. Gauges are also each connected to a circuit board with buzzer. The circuit boards have a few unused terminals so maybe one of them is for a different set point.
I will see about communicating with VDO.
Thanks for the separate alarm thought. I too like the Borel high exhaust temp. option.
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Old 07-30-2016, 01:30 PM   #14
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Hi Ski,
Thank you very much.
I'm learning a lot and have to find some of those ports and the oil gallery (whatever that is) and get to work. What is a snap disc switch?
All you guys have been great helping me along and broadening my understanding of my engine and how to care for and protect it. I still have a long way to go.
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Old 07-30-2016, 02:23 PM   #15
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I would be checking that the exhaust riser is not beginning to clog. Just my 2 cents.
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Old 07-30-2016, 02:50 PM   #16
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Hi Cliff,
Good though thank you.
I plan on cleaning the heat exchanger. I'll check the riser as well.
Thanks again!
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Old 07-30-2016, 03:25 PM   #17
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Our 6BTA5.9 280HP ran at 185 degrees consistently at usual 1600-1800rpm (7.5kt). Never went above 190 even in the Bahamas. Mind you I never ran at WOT except at sea trial!! Even then the temp. alarm stayed silent. Before doing anything more complicated, suggest you check your impeller condition. Lose a few vanes and it does not pump so well!! Hard to tell by just looking at exhaust flow.
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Old 07-30-2016, 04:35 PM   #18
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I think Ski gave you good advice and offered a comprehensive solution. Let me expand a bit:


The Snap Disc switches he mentioned are on/off temperature switches. You can buy them in many configurations: normally open, closed and at various temperature switch points. You can build a very inexpensive alarm system by using one clamped on the exhaust, another for the block and then a temp switch plugged in where Ski suggests and an oil pressure switch and a 12V buzzer all of which are available on Amazon.


But if that is too much do it yourself, you can start with a basic Borel exhaust temperature alarm system for about $100. It has a nice panel mounted alarm, a 165 deg alarm switch that clamps on your exhaust hose, and wiring to hook it all up.


Since the Borel alarm switch is a simple, normally open set of contacts that shorts to ground when you hit its alarm point and completes the 12V circuit and sounds the alarm, you can daisy chain more switches to the same alarm such as a Snap Disc for the block and the pressure and temp switches that will replace your VDO circuit board. Then you will have a comprehensive alarm system that will do much more than simply alarm high coolant temps which may be too late.
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Old 07-30-2016, 05:18 PM   #19
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Listen to Ski and David for the best advice.
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Old 07-31-2016, 06:29 AM   #20
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The Murphy gauge alarm is adjustable to what ever temperature you desire and will trigger an alarm .

Made for pressure , temperature , basically anything you wish to monitor , they are a great investment if you just have a lookout underway , not a trained crew member.
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