Max rpm on a 1996 evenrude E150ELEDB

[tjspei]

Hi

I am trying to figure out what the max rpm is on a 1996 Evenrude 150hp E150ELEDB. My boat is a 1976 18ft and the engine is maxing out at 4200 rpm. I am not sure of the prop pitch but my boat jumps on plane REALLY fast it just wont go much past 4200rpm. I think my boat mechanic doesn't have the throttle cable set up correctly and it should have some more top end. Also that top RPM doesn't change much if its just me with a half tank on the boat or 2 guys and fishing gear with 2 coolers full of ice and a full tank of gas.

Thanks
Tim