Cant add any more extension, it is allready maxed out. Risers are 5" taller than normal, and extended to the transom. Cam is only 230/236 @ .050, 112lsa.

Well, that could explain it. At least that's not a difficult fix.

Those pics of my elbow extensions where not the final version., but shows the general layout. ended u with 25.5 inches with a 60 deg angle cut.

The regular alum Eddie Marine added 3 to 4 inches height over stock. Which made did NOT stop the reversion. Reversion is a result of pulses of exhaust, not from water just being able to go up a pipe that doesn't have much slope. A bigger slope might help keep a slug of water from coming in from a wave a little better. but as far as reversion, no does NOT stop it. It purely took a certain amount of 3 inch exhaust pipe length to solve it. Nothing else did, and the 25" inches or so of 3" inch extension took it away 100 %.. You can see the reversion(salt specs) up to the beginning of the elbow now but NONE get inside the elbow. Saved the exhaust valves from short certain death, which had occurred frequently before. Hope this info helps, I've spent 100 to 15 hours building and testing with the exhaust to get the reversion stopped. It was continuously costing me valve trains. Many people think motors are "normal" to rebuild every few years. They should last much longer. It's always water leaks, REVERSION, detonation from running regular when you should be running premium, bad gas, enthanol, water in gas, overproped, etc. that gets you. Motors should last a long time.

Side note. I see your intake has an exhaust crossover. If you have electric choke, look for blocked (with steel) exhaust crossover intake gaskets. Will get you a little more hp. It’s just something i do because my opinion. If heated choke (rod and spring on intake) i get blocked off gaskets and drill one with a 1/2” hole or so.

Are you then running rubber exhaust hose over this setup?

Cheech, yes, from the elbow to the 4" exhaust tips at the transom.

I am also using rubber hose in my setup, not a problem if extension pipe is aligned. You just have to mock up the exhaust without the hose, before welding the extension.

Any of you guys try running a small crossover pipe/tube to prevent reversion ?

My 2007 VP 8.1 has silly-tall risers, Corsa Captains call and a 1-1/4" crossover hose between them to stop reversion.

New season, switched to ngk br6fs. made 10min pull at 3000rpm and turned ignition off at 3000rpm. innovate dlg-1 was reading 10.3 while cruising. This makes no sense.

The Swedish 7.4L engine mod thread by "jocke" got me thinking about Jani and his engine ordeal.
I can't believe everyone missed or ignored this post.
Jani - What is this picture? Another blown out spark plug issue like last year?
Is your boat up and running?