QSB 6.7L 380 HP ENGINE :

[DAVID A ADAM]

I have a 2016 Carver C40 with twin QSB6.7L 380 hp and was wondering what the proper engine running temperature and RPM’s should be ? I’m guessing because its a 2016 it probably has a 160 degree thermostat.
Thank you – David

Topic

[Barry]

My QSB 6.7 380 hp run between 167 and 170 at 3050 rpm in the PNW. Water between 50 and 75. Ambient 40 to 85 air temp.

[Tony Athens]

QSB 6.7 coolant temps

I just did 4 days of seatrials on a new installation of a QSB 6.7 550 that was kicking my butt on a fuel supply issue/ error codes and then engine would “de-rate at 2000-RPM-ish…..On one of the days, it made it to 2630 RPM before it backed off ( another story in itself) ………..I was close to giving up and telling my dist. to sort it out…. ………………..Long story short, on day 4.5, we found the issue ( 100% factory FU) and then engine would make it to the governor at 3375 RPM without issues ( about 76% load /a 440 HP load, nicely underpropped) …

Anyway in relation to your question and very 3 very current seatrials on QSB 6.7 420’s— things settled down at 165F even at extended WOT runs.. Our water temps here are about 60F..

[Steve Lewis]

Give this a read……….

https://www.sbmar.com/community/topic/qsb-5-9-480hp-temperature-profile/

Your exact temp will vary based on the sea water temp. But somewhere in the range that Tony indicates in his initial response. Case in point, I am in cold fresh water of the Great Lakes. My 6CTA’s ran at 154 at the sea trial but the water was REALLY cold. Lake Erie is now up to 60ish degrees and my 6CTA’s are running 158/159 @2100 – 2200 RPM.

Also pay attention to the advice given in the last paragraph of Tony’s response.

What are the ESN numbers on your engines? We can look up your engines on Quick Serve and You can download the correct spec sheet for the engine and see Cummins spec on all sorts of things about your engines.

[Author]

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