I found a Mixing Elbow Alarm

HMT2

HMT2

.
Mar 20, 2014
900
Hunter 31 828 Shoreacres, TX
Three years back I installed an Aqualarm, low flow alarm on my Yanmar 2GM. I never really thought about it, but over time at idle the alarm would go off and I would merely need to bump the throttle a smidge to get it to stop. Yesterday I finished changing out my badly clogged mixing elbow and the low flow alarm did not go off at idle. Ergo, it now will serve as my mixing elbow alarm, when it starts going off at idle, its time to check the elbow! Who knew? Here is a link to the Aqualarm. I think this is the size I put in.

https://aqualarm.net/cooling-water-...4.html?zenid=48b33ea652c807433b25ff5cc31f7569
 
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Whatfiero1

Whatfiero1

.
Mar 29, 2017
576
Hunter 30t 9805 littlecreek
That's really cool and great info. But water flow is not all that fails on a mix elbow. As you saw a carbon filled exhaust causes engine trouble even if water is still flowing. And broken exhaust would cause exhaust and water to flood boat. But continue to flow
 
HMT2

HMT2

.
Mar 20, 2014
900
Hunter 31 828 Shoreacres, TX
Whatfiero1 said:
That's really cool and great info. But water flow is not all that fails on a mix elbow. As you saw a carbon filled exhaust causes engine trouble even if water is still flowing. And broken exhaust would cause exhaust and water to flood boat. But continue to flow
Click to expand
I don't let my elbow or exhaust hose (or any hose for that matter) get anywhere close to failure. I replace them well before they need replacing.
 
Don S/V ILLusion

Don S/V ILLusion

.
Sep 25, 2008
7,477
Alden 50 Sarasota, Florida
One caution in using this as a measure of efficacy of a cooling system - a better indicator is simply watching the temperature gauge. Flow meters such as this measure rate, not volume, of cooling water. As any restriction will decrease volume while concurrently increase flow rate, this becomes potentially misleading in terms of mixing elbow condition.

Heat transfer efficacy in the cooling system is a function of volume and contact time, not flow rate.
 
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John T1594

John T1594

.
Jun 4, 2004
834
Hunter 340 Forked River, NJ
Although I don't fully understand Don's explanation, I agree with his conclusion about watching the temperature gauge. A few years back, I replaced a cracked mixing elbow on my 3GM30F and the engine run temperature came down about five degrees under all engine throttle settings.
 
HMT2

HMT2

.
Mar 20, 2014
900
Hunter 31 828 Shoreacres, TX
Don S/V ILLusion said:
a better indicator is simply watching the temperature gauge.
Click to expand
Great idea, but I don't have a temperature gauge, just an idiot light. Engine and boat are thirty five years old don't feel the need to put one in. But I agree that would be a great way to keep an eye on how the exhaust system is working.
 
JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,810
Hunter 430 Waveland, MS
Water flow as an indicator Riser restriction may not be related.:confused:

Where @Don S/V ILLusion was making the point of Heat transfer on your engine was the key.
That is the purpose of your sea water flow.;)

Since most engines are variable speed and the water pump flow is dependent on that RPM, you can only use that Flow alarm for a pre-warm up indication of near zero flow.
Why?
The engine thermostat is probably not open, for a while, on a cold start.

Or ...

Like I do mine, make sure the exhaust is burping the quench water, when first starting my engine.
I now hear and see the "burping" at 700 RPM and know it is working correctly.:)

Jim...
 
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