engine ticks ramdomly at idle, backfire thru carb when WOTing from 2800rpm

[Icefire55]

I finaly got the boat in the water after the carb rebuild, a trim hose change.

so at idle the motor seems to ping (too advanced ignition?) but it's ramdom...

It's a 84 OMC 5.7 with a Quadrajet and an Accel distributor (coil/cap in one)

When going from idle to WOT the boat seems to do it's job (getting on plane quickly) and I tryed from 2800, to WOT it, it drop to 2500rpm than backfire thru the carb.

Idle is quite rought at 900 (going to 750-1000 ramdomly) bad gasket on the intake/carb? I reused the old thick one as the one in the kit was a thin carboard one.

When the motor is hot (170F), and I shut it down, it won't start unless I give it some gas or it will rev with no fire (no gas or flooded, dunno)

I'll try to time it tomorow morning, any guideline on this ? (got a timing light)

also, putting my hand over the primairy butterfly get it to idle way better with a higher RPM. like if it was getting too much air or not enought fuel.

 

[cr2k]

Re: engine ticks ramdomly at idle, backfire thru carb when WOTing from 2800rpm

Kinda thinking bad valve or weak lifter. BUT...are the carb and distributer marine? If not then they must come off and be replaced with marine units.

Other thing to check is the advance springs and weights in the distributer (under the breaker plate). Sticking could mean not enough advance. Or sticking in advance at low RPMs. If point ignition could also be the condenser is bad.

Is this why you rebuilt the carb or is this after the rebuild?

I think the timing on that is 8* btdc

 

[Icefire55]

Re: engine ticks ramdomly at idle, backfire thru carb when WOTing from 2800rpm

Well it's a HEI distributor (coil on top), found out it was quite loose.

Can't get it to idle to 600rpm stable, it will die, playing with the advance will even keep it running at 1500 rpm with the throttle set screw backed out.

I didn't find out any vaccum advance on the distributor so I get what is playing with me it the mecanical advance or something

Carb was rebuilt, I set the idle mixture screw at 4 turns out (which is the base from the manual), reason for rebuilt was 4 barrel not working (stuck)

carb is marine (Mercury) and the distributor look for car, but I don't think it will change something.

1984 OMC 5.7, QuadraJet 4barrel carb, ACCEL HEI distributor,