?????

Have you tried swapping carbs from side to side to see if the problem follows the carb?

Exact same problem i just chased for three weeks. My issue was the screens in the fuel bowls were plugged. Secondary more than the primary so it would idle and run fine to a point or til is sucked it dry.

Not saying this is your issue but just giving a little experience. Had a car with a big motor -16an fuel line. Car would launch beautifully then nose over and couldn't get out of its own way. Had great fuel pressure at idle and when it reved up. Come to find out a spider got in the fuel line and spun a web in the -16 line it restricted that much fuel. I would start at one end of the fuel system and work my way to the other end. It may have a line that is a little kinked. Inspect everything closely. Once fuel system has been looked at I would check everything in the ignition closely and move down the line. You will eventually find the issue.

Seem backwards but in theory would work, other motor proves that. Fuel comes out of tank thru the separator, then thru pump, then to the front of a braided/AN manifold. Regulator is on backside of this manifold. Out of regulator back to the tank. Everything is very clean, all braided with AN fittings.

Before the bowl entry there are AN extensions. I believe these have small screens in them. I will take these off and both bowls and inspect. Maybe something did work its way in there. If nothings seems suspicious I will compare jetting in other carb and swap them and throw a gauge in line and check pressure under load. I appreciate the help. I hope to get this licked. Might pull the valve covers again and see if I can spot a broken inner spring aswell. Didn't notice anything when I ran the valves but maybe I overlooked. Never hurts to check.

That is actually the best way to regulate fuel, but it requires a return line to tank.

Yes, out of the regulator it returns back to the tank. My 572 in my last boat was setup more conventionally. Had a electric pump vs. the mechanicals I have now with the regulator off the pump and to the carb. No return. It did vapor lock on occasion. These motors fire on the dime every time so seems to work well.

May be hard to see but heres a picture I had loaded on photobucket.

http://s1319.photobucket.com/user/Lu...c481a.jpg.html


Actually this one you can see that regulator/manifold a bit better

http://s1319.photobucket.com/user/Lu...tml?sort=3&o=0

Since you have owned the boat, have the motors ever ran the same?