Cummins 3971678 Aftercooler O-Ring Seal Set (4 Pc) for QSB 6.7 Marine - New

Application: Cummins QSB 6.7 marine aftercooler (charge air cooler) O-ring seal set — supplier tag lists Cummins P/N 3971678, 4-piece set, for QSB 6.7 engines in the 250–550 hp range. Application per the supplier tag; not independently verified to a specific engine serial number or CPL.

Condition: New / NOS in a sealed poly bag with the original dealer parts tag. Rings are supple with no visible cuts, nicks, or set. Untested — no testing is claimed or implied.

A fresh set of aftercooler seals is cheap insurance any time the cooler comes off for cleaning, pressure testing, or re-coring — the correct seals are what keep raw water out of your charge air.

Buyer must confirm fitment by part number, photos, dimensions, engine model, serial number, and application before purchase.