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Old 02-10-2019, 11:51 AM  
firehoser75
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City: Nanaimo
Country: Canada
Vessel Name: Pilitak
Vessel Model: Nordic Tug 37
Join Date: Feb 2018
Posts: 197
When I switched from sail to our Tug, I was worried about the raw water flow. On the sailboat, I could see and hear the water flowing and therefore, was comfortable that cooling was at least happening. (I know that seeing the flow may not be totally adequate, but at least there is some flow - seacock not closed).
On the tug however, the flow exits under the boat and it is very, very difficult to know for sure that there is any flow.
So I installed an Aqualarm raw water flow alarm in both the main engine and the gen set (between the strainer and the raw water pump). It alarms instantly if flow is blocked or reduced to a level of concern. My gen set "sucked in a small fish" once and this alarm sounded and "saved the day". I shut it down before the overheat could occur or before the impeller was damaged. Clearing the fish, however, required a swim (not fun).
I also installed on both engine and gen set exhaust temp alarms. Here I chose Borel brand as they alarm at a lower temp than the Aqualarm brand, and an earlier warning is important.
Well, guess what. On our first trip after bringing the boat home (from the purchase), the main engine exhaust alarm sounded. I investigated engine temps "all over the place" using an IR temp gun, and all was very good except for one "hotspot" on the exhaust hose. This puzzled me (and a couple of mechanics I talked to) and I decided since it was a "new to me" boat, that I would service the entire raw water cooling system to gain a baseline. The cooling system was in good condition except I discovered that my "doomed to fail" exhaust elbow (see sbmar.com to learn about this) had started to fail (internal leak), was not mixing the water and gases properly causing the overheat on the hose. This situation could have (if not discovered) allowed raw water to enter the turbo or even the exhaust side of the engine. I caught it in time to avoid MAJOR damage only because of the exhaust hose alarm. Turns out to be the best $100 bucks I have spent!!
I have it from very reliable professional sources (such as Tony Athens) that if you rely on the "normal" coolant overheat alarm, it is very possible that you will do engine damage before that alarm goes off to warn you! The exhaust alarm will give enough warning to throttle back and or shut down before damage occurs and in my case saved me from big problems (at least potentially).
These alarms are inexpensive (about $100 each) and are easy to install. With them in place you will know BEFORE damage can occur if you left the seacock closed, sucked in a thru hull blockage, had an impeller failure, or are about to suffer an engine overheat from any other of multiple causes.
Personally, I don't know why they aren't "standard equipment".
Disclaimer: I am not affiliated with any of the above mentioned companies or people, just a customer.

Just my humble opinion,
Tom
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Tom
Nanaimo, BC
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