The newer drum version 45's have the same bore as the disk assembly had. The carbs are interchangeable. If your want more power and still use a drum rotor then use a K&B 45 drum assembly. All that needs to be done to the K&B unit is to enlarge the mounting holes to line up with the OPS case then you can use the bigger bore K&B carb or like I do, use a .340 bore Carl Brey carb. You may need to use 2 case(OPS) gaskets or use the thicker K&B gasket to achieve the correct clearance between crankpin and drum. A Keeley Turbo head doesn't hurt also. The exhaust timing is still a little low but the motor will still run good without changing it. Our OPS powered sport 40 runs excellent and it will run with any of the other boat around here
thanks for your input, this is exactly what I was looking for.
So the carb neck bore (ID) inside the new drum-valve backplate assembly is equal diameter as the bore inside the original disc-rotor backplate assembly? Wow, I'm surprised OPS would have limited intake volume in a completely new designed backplate.
How are the current stock rods? They hold-up okay? They are bushed at both ends.