Blown Mercruiser 5.0 Alpha. Low hours. Replacement options

[bobbert]

If remember correctly riser extension not avail because the MPI has a DRY Joint riser, ie water does not flow between manifold and riser. Check spec for riser height above water line. Ditto recommend looking at "Y" pipe attachment to inner ransom.
While your at it REPLACE the flappers in the "Y" pipe.
Good luck, and hold on for a fast ride.