Re: Problem With 454 Mags
 

Probably not water in fuel then. I would start the engine and while someone is watch the tach go over the engine wiggling wires. See if you can get the tach to bounce or the engine to stumble. If the wire to the tach has an intermittant short to ground the tach will freak and the engine will pop and fart. You never said is it out the exhaust intake or both?

Make sure you wiggle the ignition ground wire coming out of the tbolt ignition module and the wires on the back of the distributor. When this happened to me though the short was under all the black tape at the front of the engine where the harness runs down to the breaker. I got lucky and spotted it doing the wiggle test.

BT :cool:

Re: Problem With 454 Mags
 

I Think It Is Out Of Exhaust Not Sure About That Yet
We Have Done The Wire Test Alredy And The Problem Seems Like #7 Cylinder. Motor Only Has 4hrs On It.
Carbs Were New Exhaust Manifolds Are New Too
I Bought A Hei Distribtor Which Will By Bass All Electronic In Boat This Weekend. I Will Also Do Aleak Down Test Too.
Thanks For Help So Far Ideas Help Me Figure Things Out

Re: Problem With 454 Mags
 

Tryme, I wasn't talking plug wires, I was talking primary and tach ignition wires. Particularly the purple and grey ones that come off the coil and to the back of the distributor. Also the tbolt wires and ground. Follow them and wiggle them with the engine running. I don't think a miss in just number 7 will make the tach go nutz.

BT

Re: Problem With 454 Mags
 

WE HAVE WIGGLED EVERYTHING TRYING TO MAKE IT MISS
I HAVE PICKED UP HEI DISTRIBUTOR..THAT WILL BYPASS ALL "BOAT STUFF" TO TRY TO FIND PROBLEM.
DO YOU KNOW IF THERE IS A BUILT IN REV LIMITOR ON MODULES? AFTER READING OTHER THREADS I'M LEANING TO WATER IN CYLINDER FROM EXHAST GASKET. I'M LEAVING WORK EARLY TOMMORROW GOING TO RAYSTOWN AND WORKING ON BOAT....I HAVE BEER COME ON UP :rolleyes:

Re: Problem With 454 Mags
 

Did you try the main pigtail? Had mine loosen up on two different Merc motors. Pulled it apart, cleaned up both sides and coated the connections with dialectric grease. Problem solved.

Re: Problem With 454 Mags
 

No rev limit built into the TB IV modules.

Re: Problem With 454 Mags
 

well here's update
i went to lake friday after reading everything i could during week on this website
it seems i had several grimlins
1st gasket (riser) was replaced and that solved my miss problem
2nd we found loose pigtail and that sovled my tach problem
popping still continue thru carb when you throttle it
so i put my "old carb" back on and it made most of it go away so i think i'm heading down the right path.
she got to 4300 rpms still shy of 4800 i had before rebuild
but i'm happy just going down the lake until...i feel the need for speed :rolleyes:
still need some help thou
need crank pulley for 454 and i need to know the sizes if metering rod that should be stock for 1991 454 mag(rochester carb qjet)