2003 480 CE Leaking Turbo Water Gasket

Purchase last year a vessel with a leaking Turbo water gasket. Found that the stud was snapped in the exhaust manifold. Lower stud on the bottom where it’s very difficult to get at to even try to tighten with the motor as it is now. Did the best i could drilling in place and re-tapping the threads. New stud ended up being slightly deeper into manifold, must have drilled just a bit deeper to make some extra thread. Appeared to torque well and repair seemed to be fine.

Have gone thru half the season and now appears that gasket is leaking again. Used the new graphite gasket, sealer etc. Im 70 miles away from my home port at the moment so im not touching anything since i appear to have lost appx. 1 quart during trip. Several questions:

1. If stud is snapped again like original issue, would you suspect that the face of the turbo is not flat and causing extra stress on that stud? I used the hardened studs during the installation and the proper grease etc.

2. If the stud pulled out of manifold, it was not a perfect drill and tap job since it was very difficult to get at the back of the manifold. V drive SeaRay with very little room in that location. What are your thoughts on a helicoil. Not sure how much meatal is available in the exhaust manifold for larger drilling before I was to get into a water jacket as an example.

Appreciate any guidance. Steve