Exhaust temperature?

[eddystone]

Finally got round to installing NASA EX1 exhaust temperature alarm. So far, admittedly only at cruising revs and not particularly punching tide or adverse seas, seems to settle at 33-34 degrees Centigrade. Sensor in location as in NASA instructions. I was expecting more like 60 degrees, or am I confusing with t/stat opening. (Beta 30 with Featherstream)

 

[Slipstream 34]

That sounds normal. My Perkins 4108 exhaust temp runs 30-40 deg C.

 

[Poey50]

I have a sensor attached to the exhaust elbow on the Nanni 29 hp and normal running temperature measured there is around 22-25 deg C.

 

[VicS]

Finally got round to installing NASA EX1 exhaust temperature alarm. So far, admittedly only at cruising revs and not particularly punching tide or adverse seas, seems to settle at 33-34 degrees Centigrade. Sensor in location as in NASA instructions. I was expecting more like 60 degrees, or am I confusing with t/stat opening. (Beta 30 with Featherstream)

Yes probably.
The thermostat only controls the engine temperature by varying the coolant flow through the heat exchanger. That shouldl be somewhere between the temperature at which the thermostat start to open and the temperature at which it is fully open and depend on the load on the engine.

The temperature the EX1 sees will depend on the seawater flow rate and the amount of heat it gains from the heat exchanger and the exhaust gases. Flow rate being the all important factor.

 

[LittleSister]

From what I have read in the past your cruising load exhaust temperature does not strike me as surprising. I suspect it will rise significantly, however, when your engine is under full load.

You mention you have the NASA instructions, I have copied the relevant part of these below, together with the slightly more detailed instructions from Silicon Marine, who make and sell a range of exhaust temperature alarms. NASA suggests setting at 'about 10 degrees C' above full load temperature while Silicon Marine suggests 'at least 20 degrees C' above normal working temperature, and the device default temperatures are a little different - 85 vs.95 degrees C, but I don't think these differences are significant.

NASA INSTRUCTIONS -
'(The factory default setting is 85 degrees centigrade.)
It is normal practice to run up the engine to full load and note the maximum exhausted temperature. The alarm threshold temperature can then be set a few degrees (Usually about 10 degrees centigrade) higher. It is important however that the threshold temperature does not exceed the manufacturer's recommended limits for any part of the exhaust system.' [Emphasis added]

SILICON MARINE INSTRUCTIONS -
'Being able to set the alarm temperature lower gives you more time to respond and warns you well before exhaust damage has started to occur. The gauge is supplied with the alarm temperature set to 95°C which is ok for most engines, however setting the temperature closer to the actual maximum running temperature is preferred as this will give a quicker response and it can also detect small changes in temperature such as losing an impeller blade. It is recommended that you set the alarm temperature at least 20°C above the engines normal working temperature to prevent false alarms.
When setting the temperature first run the engine until you believe that it is up to its normal working temperature and make a note of the gauge reading, the alarm temperature should then be set to 20°C above this.'

 

[Plum]

Finally got round to installing NASA EX1 exhaust temperature alarm. So far, admittedly only at cruising revs and not particularly punching tide or adverse seas, seems to settle at 33-34 degrees Centigrade. Sensor in location as in NASA instructions. I was expecting more like 60 degrees, or am I confusing with t/stat opening. (Beta 30 with Featherstream)

Great idea to fit an exhaust temperature alarm. I don't beleive the actual reading is important. Mine is a different make on a different engine and the highest temperature I could achieve on a long hard run was 40 degrees so I set the alarm to 50.

Www.solocoastalsailing.co.uk

 

[Jamie Dundee]

A lot depends on your cruising revs. Mine registers around 35c at 1500rpm going up to 47-50 (depending on sea temp) at 3000rpm. It’s surprisingly sensitive, add or subtract a couple of hundred rpm and the registered temp increases/decreases accordingly.