Hi Mark, yes the hole is oblong as itís part of the upper housing that is common between all 3 different Bravo drives. However the wood is a make shift filler. Under Documents of this site you will find the Mercruiser manual for Bravo drives and it will have the correct filler and which way to position it for the Bravo 3 application.
1997 2400 SCR
5.7 Vortec / Bravo 2