Picked up this ski and the PO said it would not run well. I pulled the carbs and rebuilt them. Pulled the reeds and cleaned debris from the rubber carb stack tubes. I tried to get it to run and had no luck with what appeared to be no fuel flowing to from the carbs through the venturi. I bought a second set of carbs used and tried them, same issue. I tried a bunch of things to get the carbs working. I pulled the return fuel line and ran it to a gas can. I put a new return line back to the fuel tank and pressurized it with a compressor. I also ran a new fuel line without the primer bulb in the system. (There was a primer bulb and primer jets installed in the unit). I got it to fire with almost completely closed choke and throttle wide open. But it would not run when the choked was opened regardless of how warm the engine got or if I tried to let off the gas to idle. Also I could see fuel flowing on the forward two carbs, but not the rear carb. I poured gas directly in the rear carb and it appeared to run a little better, but still not without being mostly choked. But no matter what I could not get it to run without playing with the choke and throttle, at some point it would always die. It would occasionally backfire to the point the exhaust got really hot. Also I never got any fuel in the gas tank I had the return line going to.
The pickups in the gas tank could be clogged as each has a filter. Pull it to see and then work your way back. If by chance you have an electric fuel pump(12v), hook it to one of the lines(perhaps at the filter before the carbs) and see if it will draw fuel. If it can, more than likely the fuel line is OK. Could be the fuel selector too.
It will not flow gas through all the carbs and run, but only when I pressurize the gas tank.
Sounds like the needle and seat on one or more carbs doesn't
like to open or reopen.
Often this is misdiagnosed as a fuel pump problem.
When you took apart the carbs, did you find any problems?
Were the float diaphragms stiff? Did you replace the float
diaphragms? Spring? and what is the lever height?
I rebuilt one of the sets of carbs and bought the other from someone that said it worked. Both sets of carbs had the same issues. But in the one I rebuilt I did not measure any lever hight. I just installed the replacement parts.