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Old 10-08-2008, 20:42   #1
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Pyrometer Recommendations

I have twin 400 turbo 6V53 Detroit Diesels with 2900 hours in the boat that I just purchased. I would like to add pyrometers to my gauge set to monitor heat before the water temp goes up. Does anyone have any recommendations for a good reliable Pyrometer at a reasonable cost? Do any of them have alarms?

Also, from what I have read, it seems that the best location for the sensors is in the exhaust manifold ahead of the water jacket, rather that at the turbo outlet. Do I have this correct? Do you need to drill and tap the manifold?

I am a little concerned that I am not getting the 2400 RPM under full throttle cruising as the engine manual said the engine should reach. The surveyor indicated that he thought the prop size was wrong, but after he checked the calculators, he reported that the props were properly sized for the size and weight of the boat. It seems that a pyrometer would tell me if I had a problem or not because if the engines were being overworked the exhaust temp would rise significantly. I am also not certain of the accuracy of the tachometers. One reads higher than the other when the engines are synched. I think the surveryor said that the lower reading was the correct one when checking with his hand held tach down in the engine bay. I am not sure if I have a problem, or not.

Dave

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Old 10-08-2008, 21:11   #2
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Having a familiarity with pyrometers, I would contact Detroit Diesels' Tech Department. Or if You have a Johnson and Towers Distributor near you, contact them.

Pyrometers are a good thing, if you understand what they are trying to tell you.
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Old 11-08-2008, 08:53   #3
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Pyrometers

Please explain. We had them on our big tractors, and I was always told to watch them more than I watched the water temp.
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Old 11-08-2008, 18:54   #4
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A pyrometer (fire meter) measures how hard the engine is working.

The greater the load the higher the temp.

It will tell you that the engine is being over worked (on its way to over heating) quicker than the water temperature gauge will.

There are numerous descriptions of the operation online if you Google "Diesel Engine Pyrometer"

I had these on Tugs....the current vessel I am Chief on has one for each cylinder of the Paxman Diesels for a total of 32.

An 85 foot sailing yacht, with twin Gardners had them....the pyrometers told us when we had the props pitched at an optimum position.
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Old 12-08-2008, 10:24   #5
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Thanks. Tha is how I remembered them and I also read the information on the web. With one per cylinder, you could tell if you had a bad injector, couldn't you?

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Old 12-08-2008, 20:55   #6
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Yes you could.

Invest in a hand held ifrared heat gun too. Raytec makes a good one. Not 'spensive.
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Old 12-08-2008, 21:29   #7
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My only experience with pyrometers is in trucks and the location didn't really matter too much. Whether it was before or after the turbo just affected what the temp. reading was, but you could see if it started to rise in either case. On a marine application I think you are right that you would want it ahead of where your cooling water enters the exhaust. Not knowing if your props are correctly sized, or if your tachs are accurate I am not sure how you are going determine what the proper pyro temp is at cruise. I would talk to the Detroit dealer in your area and see if they can give you some guidelines for the 53 series. The rise in pyro readings was always pretty immediate and dramatic in trucks when you were pulling a hill and you had your foot into it too far (lugging). IIRC normal was about 900F before the turbo and 1100F after under load, but that was with Cummins and Cats.

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