Ryanw10

Need some help with a no spark condition and a 1993 Mercruiser 5.7 I'm working on.

there is 1 black wire plugged into the back of the distributor that was not connected to anything. They only spot I found that it could maybe go is to the white wire with green stripe on the safety switch.

I have no power at any of the 4 wires that are plugged into the coil. (Purple and gray on 1 plug and brown and red on the other) The purple wire is currently connected to the black wire on the safety switch. Brown and red wire both go to the distributor. I am unable to trace the gray wire but it appears to go the main connection plug.

SB

iTrader: (1)

You say delco, but
Do you still have the Thunderbolt dist set up ?

If tbolt iv so we’ll get you a wiring diagram to go by with a description ad your wiring would be really messed up. Ex: Purple is ign+. Gray is tach/rpm. White/red power to dist sensor. White/green signal from that sensor. Black is ground.

Diag for Tbolt IV.

AllDodge

iTrader: (1)

Unless you have an Alpha drive the single black wire should not be connected to anything. If you do have an Alpha drive then the wire is connected to the shift interrupter switch

There should be power on the purple wire. This is for a 4 cyl with Alpha drive, and yours is wired the same

Ryanw10

It is an alpha drive and definitely not thunderbolt. I have plenty of those ignition systems here and this is not it. I guess I cant confirm its delco but that's what a quick google search told me. I hooked the black wire from the distributor to the white wire with green stripe on the safety switch and still got nothing. I left it hooked up and then wiggled the ignition breaker on the dash and now it fires right up for me.

SB

iTrader: (1)

Look at All Dodge's diagram above. If it's that dist, it's the GM/Delco/Merc Voyager/EST system.

AllDodge

iTrader: (1)

Your issue is there is no power to the purple wire, figure out why its not there. The purple comes from the key switch

Ryanw10

It is just like the diagram all dodge posted. I appreciate the help guys.

Ryanw10

Ok, so I got this boat running and had it out on the water but its backfiring through the carb under load. Cap and rotor are new, wires are new, I cleaned/rebuilt the carb and i have a steady 5 psi of fuel pressure at the carb with no air bubbles visible through my fuel pressure test clear hose set up. The motor starts up and runs fine up to about 2500 rpms then it starts shaking and once you get into it more it backfires through the carb.

Here's where it gets wierd (maybe). I was getting some smoke and a burning smell from the engine compartment and for the life of me could not pinpoint the origin. I narrowed it down to the front of the motor so I got back to the dock, shut it down, and the alternator was burning hot. Almost to hot to touch. Could the alternator be the source of my backfire sending funny voltage to the ignition module? It didnt smoke at idle and would start smoking really when the motor would start to shake...

The alternator is coming out today and getting rebuilt.

AllDodge

iTrader: (1)

If timing is correct backfire at higher rpms is classic for lean fuel mix, need to check adjustments and if all the channels are clean

Start the motor and get it to 1500 rpm then let it idle down. Measure the voltage at the ALT, it should be 14.5V, if its higher the Regulator has gone out. If its lower, make sure you don't have a weak battery. Shut motor down and measure battery

SB

iTrader: (1)

Yes, alternator can cause driveability and performance issues. Get this fixed before possibly chasing nothing. Always fix known issues first.