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Old 01-10-2015, 16:28   #1
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Exhaust water temp alarm?

my kabota diesel tends to overheat at 2200 rpm and up. have investigated just about everything. I'm wondering if an exhaust water temp alarm might be the early warning I need rather then staring at the engine temp gauge. good idea or bad?
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Old 01-10-2015, 16:47   #2
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re: Exhaust water temp alarm?

Which version is it, and what diameter is the heat exchanger? Universal engines with the 2" heat exchanger tend to display this symptom, for the simple reason that the heat exchanger is inadequate.

I upgraded mine to a 3" version, and can now run at full power all day, at 170F. Previously the limit was about 2K rpm, to keep the temperature under 185.
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Old 01-10-2015, 16:54   #3
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re: Exhaust water temp alarm?

If you log the temps in and out of both cooling circuits you'll find the culprit. I use a handheld IR temp gun. Cheap and non contact.

Overheating can be triggered by flow that is too slow or too fast. Heat exchanger capacity, corrosion buildup, collapsed hose (on the inside), low fluid level and faulty thermostat are all candidates too. All these can be diagnosed from logging temps.

If you find that both circuits have a relatively even temp delta but temp keeps rising then a bigger heat exchanger is probably a good solution.

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Old 02-10-2015, 08:44   #4
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re: Exhaust water temp alarm?

Make sure the engine is actually overheating by directly measuring the thermostat housing or similar coolant area with an IR gun. It is common for gauges to be wrong - and they often start creeping up in measurement as they go bad - when they rail on high.

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Old 02-10-2015, 08:55   #5
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re: Exhaust water temp alarm?

I installed an Aqualarm flow switch to the output side of my seawater strainer, prior to the seawater impeller. If a plastic bag blocks the seawater intake, or the impeller throws a blade, I have an early warning that the engine will shortly overheat. I have also rigged an LED light and a piezoelectric buzzer above the engine temp gauge to reinforce this message. Plus, I use the idiot light switch with a different color LED and different frequency buzzer to tell me when the actual temperature has gone up to a nasty point. These allow me to know that things are getting awkward even if I'm off watch and blissfully dreaming. Obviously, these are powered by the engine ignition switch.
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Old 02-10-2015, 08:55   #6
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re: Exhaust water temp alarm?

I recently fitted an exhaust temperature alarm to my Beta 50. I have had no overheating problems, but experienced the advantages of an exhaust temperature alarm on a gen set while doung a delivery. I wrote a short article for the Beta forum. Mr Feinbaum, the Beta guru agrees that it is a good idea. The cost was about $ 60, and 1 hrs work. Cheap insurancw
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Old 02-10-2015, 10:14   #7
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Re: Exhaust water temp alarm?

Quote:
Originally Posted by Dave22q View Post
my kabota diesel tends to overheat at 2200 rpm and up. have investigated just about everything. I'm wondering if an exhaust water temp alarm might be the early warning I need rather then staring at the engine temp gauge. good idea or bad?
Hi Dave,

There was a similar thread back in July this year where I detailed a cost-effective approach ($10 waterproof sensor strapped to the outside of the wet exhaust hose...)

See: Raw Water flow sensor switch alarm

In case that is useful to you.

Cheers!

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Old 02-10-2015, 10:20   #8
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Re: Exhaust water temp alarm?

Our boat has high temp exhaust alarms on both the genset and the Perkins main engine. It rings a loud bell. It also has a raw water flow sensor, and a high temp oil sensor, all to the bell.
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Old 02-10-2015, 13:49   #9
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Re: Exhaust water temp alarm?

Quote:
Originally Posted by Bill Robinson View Post
I recently fitted an exhaust temperature alarm to my Beta 50. I have had no overheating problems, but experienced the advantages of an exhaust temperature alarm on a gen set while doung a delivery. I wrote a short article for the Beta forum. Mr Feinbaum, the Beta guru agrees that it is a good idea. The cost was about $ 60, and 1 hrs work. Cheap insurancw
There is a lot of good advice here so far.

I have a Beta 60 and no overheat issues so far, but I agree that an IR temp reading of the circuits will rule out an obvious fix, AND that an exhaust overtemp alarm is good for things like taking a fish or a plastic bag over or into the intake, enough to restrict flow and cause an overheat, but not enough to actually kill it.
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Old 02-10-2015, 13:50   #10
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Re: Exhaust water temp alarm?

Waiting for an answer to my question about engine model.
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Old 02-10-2015, 16:37   #11
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Re: Exhaust water temp alarm?

Probably not but possible that a raw water impeller has collapsed at some time and the separated fins have gone downstream somewhere and caused a partial block in the exhaust water flow.
For this reason impellers should be replaced periodically as a matter of course. Every couple of years maybe for the average yacht. More frequently for high annual hours.

Disclosure. I am as guilty as hell on not doing this, but will in future.
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Old 03-10-2015, 07:41   #12
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Re: Exhaust water temp alarm?

thanks for all the good responses. I'm sold that it's cheap insurance with no downside. will post conclusions after a few months of use. I've also ordered a temp gun to double check the gauge readings.
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Old 03-10-2015, 08:18   #13
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Re: Exhaust water temp alarm?

The temp gun has other cool uses as well: Shoot it at a bronze thruhull to get ocean water temperature. Shoot it at the cutlass bearing to determine, without getting on your hands and knees if it's overheating. Play it over the connectors and breakers inside the electrical panel to see if anything is overheating. Use it to check the oven thermostat. I love mine.
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