The olds motors were VERY popular in the old jet boats. I'm not sure why. Both the green and brown boats had BB Olds in them. I had a 454 Chevy.
I'm not sure how long an olds will hold together turning 8000 RPM. You will need all good forged internals... balance all the rods/pistons... windage the lower, and valley.... put on a rocker girdle... and use roller cam/lifters/rockers.
Even then... I don't know if you can get enough spring tension, to close the valves fast enough. (you may need Ti valves to make them light)
If you have noise issues... we were all running Basset wet boxes. They exit out the transom, just at/under the water line. That helped keep it quiet at idle. Mine were cast aluminum, and had a hump in them, to keep the water from flowing in.