I think you should put one of your 500EFI intakes on that engine and see what it does!

I actually have two of the old style large screen flame arrestors this five layers of screen and cause I took a torch heated to go up and took all of the layers out except for the outside layer it will appear to be a factory flame arrestor but should pose very little restriction I will be dining with that by the end of the week and see what happens

Why do you think it made so much more power than a 500? Could it be because you turned up the max RPM over 5250?

Huge throttle body, highly modified intake, keep in mind i made over 650hp with this intake on a 8.3 to1 540 w huge cam and afr heads in past and 1115 hp blown on a diff dyno, we are also using j607 CF which most shops use but reads 3.9% higher than mercs 1349

How much does wet headers and running accessories cost in power?

Yea I know I asked before, and my smashed flame arrestors cost me 10hp also.

Im going to say 30 to 40 hp, not positive though, for the guys w stock 502s that are thinking of doing some of these mods keep in mind even though this cam is "small" hp 500efi, it wouls STILL revert with stock 502 manifolds from what im told, this motor is getting a set of gills when it goes in boat

Here is the gutted out eralier style flame arrestor im trying thurs or friday

Mefi 3 controller, i have a unlocked innovation hp 500 tune left from tuning blackhawks pantera and a mercruiser hp 500 efi tune, neither one would rev past 5700 however no matter where you set the rev limiter so i ended up using a old mefi3 blower tune i had that did rev and manually transferring all the fuel ,spark, iac, idle, tps, flags and scalars tables into it, now motor revs to limiter at 6100. It drops fast after 5700 though since cam is small and intake runners are still a mile long but it does carry well to 5700

Equalizing the back pressure on this exhaust with the long collector should gain you some pony's also, put some zoomies on it and let er rip

Is that my high performance harness on that beast LOL............good for 20hp

On a 540hp 502 standard riser full wet Gill Exhaust with tiny cam......drum roll....about 10 hp. About 14hp with all accessories including sea water pump. Shocking huh ? LOL.

As cam (overlap - which is considered the 5th cycle) get's bigger, exhaust always get's more important.