Mercruiser 5.7 quadrajet sputters at 3900 rpms

[othelloears]

Just installed rebuilt 1984 Mercruiser 260 5.7 350 (supposed to be 280 hp) in my Wellcraft Elite 200 with a rebuilt carb. The engine starts, idles and runs perfectly until try to go over 3900 rpms when it sputters pops and won't go any more. Its got new plugs, wires coil cap ect.. New fuel and filters. Checked the pump and seems more than adequate. Timing is spot on

Pretty confident at this point its the reman carb. Thinking not enough fuel. Hoping its just a secondaries adjustment but thinking its secondary rods and or jets. No ida what the rebuilders put in there.

Main question...does any one have the carb specs for jets, rods ect...?

Second question for quadrajet guys...assuming its actually 280 HP as advertised should I increase stock 260 specs for jets, rods or both.

 

[81 Checkmate]

Re: Mercruiser 5.7 quadrajet sputters at 3900 rpms

After you get the carb straighten out.....if it still dont check out. Another option... check to make sure you dont have a worn cam shaft lobe.

Ours was doing as you described...no top end and it was sputtering and poping after 3OOO RPM.

Happend on the 81 - 305.....had to replace the cam and lifters....after that all was good.

Good Luck!

 

[81 Checkmate]

Re: Mercruiser 5.7 quadrajet sputters at 3900 rpms

Scratch that......Just seen that you have a rebuilt motor!

 

[othelloears]

Re: Mercruiser 5.7 quadrajet sputters at 3900 rpms

Ive done some more research and pretty confident its the quadrajet setup. I am trying to find out fr the rebuilder the differences between this and a stock 260 so I can try and figure out what jets, primaries and secondaries to start with.

Any quadrajet people out there who can give me a recomendation for a starting quad setup for a 260 bored .30 over with a cam upgrade? the books lists a 260 with 067/041 CL. Seems like I woulnd't have to go to the MAG setttings of 069/036 CH?