Trimming Jacuzzi A to C

[justaddfuel]

Hey, guys. My boat has a Jac 12wj with an 'a' impeller. I bought a new GM Performance small block 290HP. Power's pretty flat from 4900 to 5100 rpm, around 290, hopefully. I'm using GM's dyno #s here. Should I cut the impeller down to a 'c', 9 1/4", and should I cut the same angle. I understand a jac 'c' is close to a berk 'b'. The boat's a 16' flatbottom, mainly for skiing.
Thanks.

[Floored]

Personally I'd try a B first and get a feel+ a little tuning time before a bigger cut. You can cut more later but its hard to weld those chips back. Boat is a 16 so it may work for you. Jac B is a berk A. Once you have a baseline of rpm then you can go to the pump person and give him data on rpm with your combo and make a well informed decision. What intake, carb and exhaust do you have with it?

[malcolm]

Most WJs have Bs in them. If it really is an A, don't cut it, trade with me for a B. :D My 455 needs the A.

[justaddfuel]

Floored, the intake is an Edelbrock Performer, carb is Holley 600, vacuum secondary, exhaust is custom 1 1/2" square tube primary, 3" collector, each flowing through a Walker Evans muffler. Exhaust is dry. Ignition is MSD, Hei style. Cam is 222 intake and exhaust @0.050", 450 intake, 460 exhaust, 114 lobe seperation.
Malcolm, it's definatley an A, 9 9/16", this boat had a 454 in it, but it's going to take a 1/8" cut just to clean the blades up. She's going in the water next week...Holidays.

[Floored]

that setup should help it pull good in the rpm range your looking for. give her heck and let us know how its working.