They were sold to racers only. Most were on the Merc race program. I owned a set and put them in my personal boat and Merc did not like that too much but I got away with it. There were two types. A 542 Cu In and a 500 for class one. The Merc 900SC is basically the 1000 without the need for av gas and a little less boost along with some small other changes. I think I still have the specs for both types if you need them. Just let me know.