Tidbit: Engine exhaust hose temperature monitoring [Updated Jul-2023]

This is one of a series of brief, no nonsense posts that we call aTidbit: 

noun; small and [possibly] particularly interesting item of gossip or information...

The purpose is to share succinct posts about lessons learned, or things we use or do that work [or don't...] that are common to most of us boaters. 

The goal is to garner feedback from those of you having first-hand experience with a different approach/ solution/ product/ or additional useful information to share...  

We never assume what we are sharing is the ideal or only; it just seems to best suit our needs [and/or habits and/or budget] from our experiences thus far...

Sometimes these Tidbits originate from a topic of discussion on one of the forums we participate in, and this happens to be one: Link to original forum post [31-Jul-2015]

Note: The original blog post [below] has been inducted into Tidbits since it qualifies, but was published 3 1/2 years before we initiated the Tidbit series...

                   ➛ ➛ Peruse the right-hand sidebar for the up-to-date list of Tidbits ➛ ➛                  

Original Question from Cruiser's Forum:

Re: Raw Water [exhaust flow sensor switch alarm

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Quote:

Originally Posted by kevins  I am thinking about putting a flow sensor/switch/alarm inline between the raw water intake pump and the heat exchanger. Has anyone done this? Any luck. I believe it will help me recognize an overheat before it happens. any thoughts? thanks kevin

Hi Kevin,

With wet exhaust systems there are two basic ways to monitor the presence of sufficient cooling [injected raw] water: water flow (as you describe) and internal or external temperature of the exhaust hose.

I chose the external monitoring method for simplicity and cost effectiveness. (No sensors inside the caustic exhaust hose environment- its bad enough on the outside...)

Another reason I chose this approach is because flow of raw water at the injection point does not necessarily mean enough water is being injected to keep the exhaust tubing at desired temperature. [e.g., What if your exhaust elbow is constricted and not allowing enough water to be injected...? A not uncommon problem prompting annual inspection and cleaning of our exhaust injection elbows as part of our PM process...]

I bought 3 submersible thermistors [extreme environment waterproof and potted] from the manufacturer for about US$10/each and put one on each engine and generator wet exhausts, with one for a spare...

For details regarding this DIY approach, read the excellent article John Lewis wrote last year published in Ocean Navigator magazine.

I hope you have fun with your project.

Cheers, Bill

SV Denali Rose

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Additional Resources:

• Fitting a commercial exhaust temperature alarm 
• Silicone Marine exhaust monitoring systems [UK]