Logo

1979 Chris craft mercruiser 454

Smittymonster

New member
Hello everyone I bought a Chris craft with 2 454 mercruisers I’m replacing cam an lifters in port motor now I’m having issues with STB motor which is a reverse motor an has a mercruiser IV firing system. I have fuel I have spark I have oil pressure seems to roll a little slow but does try to fire but won’t actually fire all the way an run I have checked firing order I have replaced plugs wirers coil. What else do I need to check an or look for ? Thank you
 
If you have fuel and spark, you also need compression. Refining the list of essentials, I'll add you need a water-free combustion chamber and to make sure the spark occurs at the correct time (initial timing).

Being as you've said nothing, I'm assuming the starboard engine had some level of work? if so, wanna share that list?

are these carb'ed or EFI? separate or shared fuel tank(s)?
 
If you have fuel and spark, you also need compression. Refining the list of essentials, I'll add you need a water-free combustion chamber and to make sure the spark occurs at the correct time (initial timing).

Being as you've said nothing, I'm assuming the starboard engine had some level of work? if so, wanna share that list?

are these carb'ed or EFI? separate or shared fuel tank(s)?
So they are carb I have pulled them from the tanks due to I had to clean and polish them which is done but for now I’m using a 11 gallon portable tank with fresh fuel rec 90 with a fuel an water separator inline before the carb with B12 chem tool treatment. The motor has had work done compression is good seals have been replaced heat exchanger has been replaced they have had the mercury IV electronic ignition added to them new plugs new wires new cap. We have fire but seems like there is a few seconds between each spark on number 1 cylinder plug the motor is also turning over slowly an pulling a lot of power from led lights an gauges to fluctuate.
 
have you pulled the aft-most pair of spark plugs to make sure water isn't flowing in from the exhaust?

Also, you say you have spark - is it a good clean snapping blue spark or a weak quiet yellow spark?

Are the cap and wires OEM or aftermarket?
 
have you pulled the aft-most pair of spark plugs to make sure water isn't flowing in from the exhaust?

Also, you say you have spark - is it a good clean snapping blue spark or a weak quiet yellow spark?

Are the cap and wires OEM or aftermarket?
I have checked each cylinder only fuel is getting in them no water. Stock cap a rotor after market wires but there proper ones got them from Napa also changed the coil out had them run a check a replace it which is also from Napa. I was just down there an playing with adjusting the degree on the distributor an I think I have a bad connection in my wire from it to coil because it would sound weak an slow then mess with it an speed up an sound loud when I mess with the wire an turn it out to fare. So I think I need to start there maybe an just put an hei on the motor.
 
I have checked each cylinder only fuel is getting in them no water. Stock cap a rotor after market wires but there proper ones got them from Napa also changed the coil out had them run a check a replace it which is also from Napa. I was just down there an playing with adjusting the degree on the distributor an I think I have a bad connection in my wire from it to coil because it would sound weak an slow then mess with it an speed up an sound loud when I mess with the wire an turn it out to fare. So I think I need to start there maybe a just put an hei on the motor.
Also it’s a good snap of spark can’t be honest on the color it’s been hot an I been covered in sweat but I do know it will spark then if you count 1,2,3,4 then it sparks again I’ll head down there in a bit an check the spark
 
you can always check the spark coming out of the coil....
Ok I’ll check that I definitely know I have a bad connection between the coil to distributor because I trusted the distributor out a little farther to get it to make that noise again an when I mess with my one wire it goes slow an soft sounding an mess with it again an it gets faster an louder. Could that be a problem should I just put my accel hei one on ?
 
I'd guess it is easier to fix a wire than to swap out the entire distributor...but its your call there....just make sure the ACCEL HEI unit is marine rated...
 
I'd guess it is easier to fix a wire than to swap out the entire distributor...but its your call there....just make sure the ACCEL HEI unit is marine rated...
I’ll fix the wire for now but I’ll be swapping it out once I know it runs because the electronic firing system is out dated a can’t really get replacement parts for it. Is there anything else I should check.
 
I'd guess it is easier to fix a wire than to swap out the entire distributor...but its your call there....just make sure the ACCEL HEI unit is marine rated...
I did check today I have a snappy yellow spark does that mean I’m not getting good feed or is the coil weak some how I just put this coil on 2 months ago.
 
The TB-IV systems generate a crisp blue spark when the are functioning correctly...likely bad connection in the +12VDC feed to the coil...
 
Depending upon the serial number and the specific version, there may have been resistance wire in the harness...if the jumper Bondo described makes a difference, it may be worth checking into...
 
Depending upon the serial number and the specific version, there may have been resistance wire in the harness...if the jumper Bondo described makes a difference, it may be worth checking into...
I can try to get the serial number I do know there’s a solenoid on the very back of my motor which I thought was a very bad spot for it.
 
Depending upon the serial number and the specific version, there may have been resistance wire in the harness...if the jumper Bondo described makes a difference, it may be worth checking into...
So I found I have 2 red wires tied into one red wiring leading to my + on the coil I just tried my coil also from my port motor which it ran till it dropped a lifter so I know it’s a good coil I changed the ends out to new ones with heat shrinks to make sure nothing is arcing.
 
That means somebody has been into the engine harness...hopefully, they used tinned wire and sealed connectors....
 
That means somebody has been into the engine harness...hopefully, they used tinned wire and sealed connectors....
Ok just a stupid question I’m looking from the back to the front of the motor all my pulley an belts are turning to the right which means a reverse motor but my rotor is turning clock wise ok do they use a special gear at the end of the cam an front of the cam ?
 
Standard production GM blocks from that era that are RH'ed use a gear drive between the crankshaft and the camshaft...the distributors are the same for LH and RH engines...
 
Standard production GM blocks from that era that are RH'ed use a gear drive between the crankshaft and the camshaft...the distributors are the same for LH and RH engines...
So I got some improvements yesterday it’s struggling to fire still but with some starting fluid I can get her to actually to want to run had her rolling on her own for about 4 seconds what should I check now ?
 
So I got some improvements yesterday it’s struggling to fire still but with some starting fluid I can get her to actually to want to run had her rolling on her own for about 4 seconds what should I check now ?
Ayuh,..... Why it ain't getting any gas,......
 
Ayuh,..... Why it ain't getting any gas,......
It’s getting gas trust me I have it hooked to an external 11 gallon tank on my upper deck with a fuel an water separator an a elec fuel pump with regulator so it’s got fuel I’m really leaning it’s time for that old electronic ignition to go an drop in my hei.
 
Standard production GM blocks from that era that are RH'ed use a gear drive between the crankshaft and the camshaft...the distributors are the same for LH and RH engines...
So we found the problem we where getting bad fire to some of the plugs so we are putting the hei in an another set of wires.
 
Back
Top