Comps version of the 525 efi cam
inboard tail pipes are 6" to where the water mixes then there is a 90 and approx 47" of 4" tubing running to 6" side outlet
Outboard tailpipes are custom built 90's about 8" long to water mix, then 12" of 4" tubing to 6" outlet.

I had 3- small dams welded (12,5,7) into the spaces between the inner and outer tailpipes to help direct the water away from the inner pipe. I also extended the inner pipe 1" on the outboard 90 tailpipes.

The waters dams Im sure helped with your set up. I have twin HP500EFI's with 525 cams and recently tried those header/manifolds on my Hustler. I only had 8" of tail pipe infront of the transom before the water dumped into the exhaust stream. I had reversion really bad and had to change to another set up. #7 & #8 cylinder exhaust do not have much of a drop and my cams sucked alot of water back into the motors.

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so this is how it sounds with these headers, based on my speed and time to come into frame I was 1/4-1/3 mile away when my daughter started recording.


https://youtu.be/u5JcAOsrT_M