Checking cooling system with it all on engine. 14-15lbs 2hrs no drop in pressure only thing I’ve seen is a little drip of water off my circulation pump.

The same thing is happening with the new motors that happened with the old. Its reverting. When you ran the old motors on a hose for 20+ min no issues. Put them in the boat. Boom revert.most likely because of the amount of volume from the sea pump. Your “dry to the tip” not full dry so even with those flappers it can still revert. On the dyno its not going to revert because of the dyno headers. Pretty simple process of elimination. Didnt revert until installed in boat. Your tails are pretty flat being a converted trs boat. Thats against u aswell and can make the reversion even worse. That cam doesnt help either. But the old motors cams wernt far off of what you put in the new motors. Obviously i could be wrong but chances are the old motors were fine too. I understand they were “frankenstein” engines but they were still the same basic concept of eachother. Maybe different brand cranks. But same size. Same 088 /188 style heads. Different brand cams, but same lift/duration or damn close. Your issue is clearly related to being installed in the boat with those risers/tails and a seapump with big volume. Im not trying to hate just a opinion from the outside looking in but it appears your having the exact same issue with your new “professionally” built engines as you did with your “Frankenstein” ones. Feel free to PM me if you have any questions theres a couple quick things you might be able to try to prove my theory.

Are your tails dry to the tip or transum?

Also just to add from looking at your pix it looks like u have exhaust tips its not the tail running threw the transom? So your exhaust is mixing going into your tips? Which is usually fine in a bravo style setup but if your having reversion issues thats deffinatly not helping

dry to the tip short of the transom this picture gives a bit of a idea then it has to the tip through the tip and a boot in between. Also here is a photo showing how short it comes from the transom

yes sir you are correct

im all ears feel free to call or text me anytime. 931-247-3586

one thing you said about the volume of water from the sea pump this thing pumps a TREMENDOUS amount of water it seems to me.

Yeah man thats what im leanin to. 525 motors with full headers and tails that went threw the transom then mixed had enough problems with reversion. Further more yours being cut back and mixing then going threw another piece of pipe mixed and a flapper to keep it all in

Alex you pipe should look like this if their dry to the tip

posting these for show and tell. I guess these are “ reversion dams” ? Anyways I took a closer look at my risers and noticed they are rotted and hell even on eke the dams is just gone all together