Exhaust Temperature Alarm

[mikekomm]

I'm about to install an exhaust temperature alarm on my Carver with twin Caterpillar 3208's. There are two popular products that I'm considering from Borel Mfg. and Aqualarm. Both products use a band that clamps around the exhaust after the mixer. The Borel alarm trips at 165F and the Aqualarm trips at 200F, both of these cannot be correct for the application. If 165F is the correct temp for this application, then Aqualarms product at 200F will not trip early enough and engine damage may already be taking place. If the 200F setting on the Aqualarm product is the proper setting, the Borel 165F product will set off early false alarms. Can anyone shed some light on this?

[hellosailor]

Mike-
Probably best to ask Caterpillar.
IIRC exhaust gas is in the 700F range, and cooling water">engine cooling water could be 140F-170F depending on fresh or salt water choice. So the 165 might be adequate, while the 200 might also be normal considering more exhaust gas in the mix means temps higher than just the water would be.
You could also take an infrared non-contact thermometer to read what your "normal" temps are in that location, now. Or a simple oven temperature/clock/timer, the kind that has a stainless probe, which could be strapped into the same location and read from time to time to see how it normally is.
The question is not which is "right" but rather, what is normal in that spot, in your installation.

[shakey doug]

By using the 165f sensor you can always insulate the mounting area in order to reduce sensitivity.

[Snowpetrel]

You could go for a TM4 engine watchdog. They are perfect for this application, with a fully adjustable alarm point, and another sensor that can go on the block to warn of early coolant loss or overheating.

I've got one on my engine and so have my folks. Its probably saved their engine, and possibly the boat a few times when they had an intermittent thermostat issue.

A good bit of kit, and I've always had a very prompt response when I ordered from them online.

I plan to order one for my car, much cheaper than a cracked head.

http://enginewatchdog.com/tm4.html

[Snowpetrel]

Or just hook up one TM4 lead to each engine exhaust mixer, and you can monitor each engine with one unit.

The TM4 isn't a pyrometer, it won't give direct Exhaust Gas temperatures, but it will give very early warning of any problem on the salt water side before exhaust damage or engine temos start to go up to much.