Monitor exhaust gas temp or coolant temp?

[Ric]

Which is better to warn of impending engine overheat - an exhaust gas guage or a coolant guage?

My engine (VP MD2020) occasionally overheats if I run it at more than 2500rpm. The problem seems to be resolved now but nevertheless I would like to be able to better understand if the problem is going to occur again.

 

[nigelmercier]

I'm considering doing both: either manually via a switch, or a device that switches between the sensors.

 

[Trundlebug]

Quite simply it's best to monitor both.

Of course, if your exhaust overheats through a fault in the flow of raw water, then shortly afterwards the engine will overheat.

However your engine can still overheat with no fault in the raw water system if the thermostat fails or there's an internal blockage or restriction somewhere.

It's not expensive or difficult to measure exhaust temp, gauges c/w sensors available for around a tenner from eBay (I'm sure someone will post a link shortly).

Most engines will be equipped with a tapping for a temp sensor so easy to retrofit that too.

Do both.

 

[macd]

As said, no reason you can't have both, and every reason you might want to. If melting your exhaust system is the worry, coolant temp would be too slow to respond to be much help. As said, components for a simple exhaust temperature alarm can be bought for around a tenner: just a temperature-sensitive switch, a buzzer and a few metres of wire.

 

[nigelmercier]

As said, no reason you can't have both, and every reason you might want to. If melting your exhaust system is the worry, coolant temp would be too slow to respond to be much help. As said, components for a simple exhaust temperature alarm can be bought for around a tenner: just a temperature-sensitive switch, a buzzer and a few metres of wire.

Much better to get one (or two) of these: http://amzn.to/1ltWKc6

 

[lw395]

A coolant temp gauge will also detect over cooling, e.g. stuck thermostat.
An exhaust temp alarm detects raw water failure.
A calorifier temp gauge tells you if the shower's good to use...

 

[KevinT1]

Nigel,

How loud is the alarm - and can you attach an external alarm.

For example - could I have 2 of these in the engine room with an external alarm in the cockpit - or even use the sounder from the existing Volvo engine controls ( MD22 )

Much better to get one (or two) of these: http://amzn.to/1ltWKc6

 

[nigelmercier]

How loud is the alarm - and can you attach an external alarm... or even use the sounder from the existing Volvo engine controls ( MD22 )

It doesn't have an alarm, but yes and yes.

 

[westernman]

An exhaust gas temperature sensor will warn of engine overload. It is essential equipment on boats with controllable pitch propellers which do not have enough electronics on the engine to give a % load read out.

 

[afterpegassus]

It doesn't have an alarm, but yes and yes.

There was a similar thread not long ago with similar displays linked. However, when I enquired of the supplier whether these could be used with a buzzer, he said they could not.
If they can, is there a diagram available for the electronically challenged?

 

[nigelmercier]

... However, when I enquired of the supplier whether these could be used with a buzzer, he said they could not. If they can, is there a diagram available for the electronically challenged?

Of course they can be connected to a buzzer. The units comprise a display, and a temperature activated switch.

To use the existing buzzer and warning light, just connect ground to one side of the switch, and the other side to the temperature switch in the engine.

Still need a diagram?

Assuming we are still discussing these: http://amzn.to/1ltWKc6