QSM 11/670 fuel cooler yes or no

[Larry Backman]

Guru question for Tony:

Can I ditch my QSM 11/670 fuel cooler. I have 3 use profiles.

1 is local running for 45-60 minutes max with a tank never less than 50 gallons of fuel. Water temp of 70-75, air temp 65-85. I’m sure I can remove it in this use case.

2. Is trolling or idling as part of a 36 hr trip which starts with a 100 mile run through that same 75 degree water/85 degree air. tank is at least half full with 75 gallons or more. I’m sure I can remove it for this use case.

3. The 100 mile run home, 5+ hours at 1900 RPM, 18+ GPH, water temp 75, air temp 80. In this use case the closer I get to home the less fuel I have. In my last hour I’m probably down to 10-20% fuel in the tank I am running from, 20-30 gallons of fuel. This is the use case that concerns me. Do I need a fuel cooler in this situation – 19 GPH fuel burn with only 20-30 gallons in thr tank?

Topic

[Larry Backman]

Good question – I have a sensor

Steve:

Great question, one I can’t answer till my first long run in June.

There is a fuel temp sensor and reading on my Vessel View, I don’t know where the sensor is in the fuel system, nor do I ever monitor it to see what it’s reading says.

I will find out where it is/what it’s reading and Will monitor it this summer to help me in making the right decision.

The fuel cooler on a QSM is monstrous and makes for a painful impeller change!

[Steve Lewis]

Hey Larry………..

https://www.sbmar.com/articles/understanding-marine-fuel-coolers/

Tony referenced this article in another post. The one about 6lp to 6bt….. Interesting info and it all comes down to the fuel temp at the input to the engine. I was thinking about this as a mental exercise and figured I would drop this note into the thread. Not sure if it is of value but here it goes………

Do you know or can you look to find a fuel temp value on your engine instrumentation? It might be instructive to know what your fuel temp is now if you can find it. On a hunch, I looked up the Maretron fuel flow instrumentation and it does have a fuel temp sensor. At least that is what I found in the online docs. If you can see that your fuel temp before it enters the fuel cooler is below 140 for your entire trip then theoretically, removing your cooler is ok.

Or maybe the SBMAR folks have a magic formula or dart board that has the answers……….

[Author]

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