There are going to be numerous reasons for their demise posted, and comming from an OMC family, I was sadened to see their filing for chapter 11 and reorganization under Green Marine, and eventual shift to Bombardier.

By 1965, OMC had the largest die cast aluminum manufacturing plant in the world and employed thousands of people.

Lets step back a bit. Around 1980 give or take, Brunswick, Mercury's parent company began buying boat companies and selling packages with their Mercury engines. By the late 80's, there was an economic shift because of the luxury tax Regan had placed on items such as Ferrari's and boats. It destroyed the small boat builders such as Switzercraft to name one. So, OMC decides to get into the boat building business when all they really needed to do was offer the existing manufacturers to pre-rig for their engines rather than dropping all the badly needed capital on another industry.

Second, you had the enviro knumbskulls pushing cleaner engines, so, oil injected motors were being made. OMC's system at first was very flawed and they ended up replacing alot of blocks that seized. Add the two and you got the beginning of the end.

Any insiders have anything to add, I'm all ears.