I have a '97 271 Fastech with a 502 Mag MPI. It currently has cast iron exhaust manifolds and risers with about a 3" spacer in between. It is also, a straight exhaust. I have a set of Gil style manifolds and risers with integrated silent choice, air actuated.
Anyways, in order to use the Gil exhaust, I would have to install a Y-pipe and some miscellaneous hardware, and get it to meet up with the Silent Thunder transom locations. Not sure if they will line up at this point.

My question is, has anyone used the gil manifolds with gil risers and utilized the existing transom cutouts? My understanding is that the Silent Thunder cutouts are different than standard Bravo cutout locations.

I have an opportunity to buy a set of gil risers but not sure they will line up.

Bob

The holes are different by 11/16"

Sorry, just realized you have a '97 boat and that may be standard bravo location

I am going to try to get some measurements tomorrow and see what it looks like.

The holes are way off the standard bravo location. . I had to relocate mine to get a standard bravo header to fit. I am talking like 3 inches not the dimension listed above. If you have a short distance between the tail pipe and exhaust hole you will defiantly have a problem. I had emi thunders with long riser at one time. Was able to use those with a slight kink in the hose. When I took it apart the hose was burnt and blistered but it worked for awhile. Once I installed real headers the hose had a major kink. Bought the highest temp hose I could find and burnt through within 15 minutes. Ended up relocating my exhaust holes and regelling the transom. Not a huge project . . I will repay my subscription and post some pics up when I have time. Jeff wurl

By the way if you have silent thunder the holes are in the wrong spot. Do not know if boats without silent thunder are in the correct spot or not . Jeff wurl

I do have silent thunder and I got a width dimension. The standard bravo width from center of cutout to center of cutout is 27.328". Mine is about 26.5"
I could not get an accurate measurement of the height though. Too many things in the way, including the Silent Thunder box on the outside. The standard Bravo for height is 13.422" above the crankshaft centerline.

I did put a call into Formula for the dimensions and they have not returned my call. It has been a couple of day.

Bob

Maybe this will help, compliments Hardin Marine.

https://www.cpperformance.com/Instru..._Locations.pdf

Good Luck

The width is slightly off but the height is the real problem . Jeff wurl