Hello, I new and have a carburetor question.
 

My name is John, Baitkiller was my father and as such is bronzed into all of my forum handles. I have browsed here for years but never registered until now. I am a long time member of THT and a marine surveyor by trade.
My question revolves around my ski boat. I have an old restored Nautique that is bit of a bastard in that she runs a left handed Chevy instead of the Right turning Ford.
I recently replaced the long block from a 1990s 5.7 12 bolt intake engine to a Vortec that by all accounts should make a few more horsepower.
I have the thunderbolt 5 and merc Weber 4bbl.
The old motor ran like raped ape, the new one seems like it runs out of fuel over 4100RPM. It will gain power if I back off the throttle when wide open. i cant even pull one barefooter let alone the three I could with the old motor. Timing is full in at 32* and 3700. I have run on a shop can with no change. Carb has been gone through, new fuel pump installed. new cap and rotor, new wires and coil are ordered. The only thing I have left is jetting.
? Do the vortec heads flow that much more air that I need to drastically re-jet or replace the carbureter?
Advise or suggestions please.
Thank you,

Edit: I tired to correct the poor grammar in the thread title but have been denied. Sorry Mrs. Wilson, (4th grade English) I tried.
John

Curious, what direction are you running the new motor ?

Guessing you don't have a wideband 02 to check the A/f ratios, did you check any plugs for color ?

left handed.
No gas analyzer.
Plugs look a little too clean, light grey, not deep tan.

Everything is the way it was on the old motor which ran bloody great until a valve seat fell out and ended the party. The only changes are that the new engine is vortec. It runs great but has no real power, especially on top but mid range pull is weak too in comparison.

What was the HP on the original motor compared to the Vortec, how close are the cams, I don't think all of the Vortec's were high performance.

Standard 5.7 alpha should have been 280 with the tall GM intake and 4bbl. The new engine I did not build but was t(s)old it should make 340 ish with tall intake and 4bbl. I have no idea what went in it camshaft wise. Both are roller.

Thinking cam specs would be the place to start, if you can get your hands on them. It might just be under cammed and dying at 4100.

Thanks

you need to put a fuel pressure gauge on it to see what its doing from of idle to wide open, also check the timing for full advance