Making sure I purchased the correct coil for a 1996 5.7L

[Ed Harris]

I purchased a coil for my 1996 5.7L and the boat has seemed under powered since The swap. I installed a Sierra 18-5438. Would this be the correct one for my engine # 0F790518?

 

[alldodge]

Yes coil is correct
Coils usually never go bad, most likely have something else going on

Explain why the change?

 

[Ed Harris]

The old coil was rusted and appeared to be the original. Since I had the engine out replacing the broken ring gear on the flywheel I decided to change the coil.
I have not done a tune up on this engine since I have owned it. I bought it 3 yrs ago.
Running it yesterday in the bay it started missing and sounding like it had an exhaust leak maybe even back firing and popping while throttling up.
Running on the hose you could tell it was missing but none of the exhaust leak sound or back firing or popping sounds.

 

[alldodge]

If module is 2 wire i would cha get it

 

[Ed Harris]

is the module the black box behind the distributor that is flat in shape? Is there a picture diagram and wiring diagram available?

 

[Scott06]

is the module the black box behind the distributor that is flat in shape? Is there a picture diagram and wiring diagram available?

I believe AD is speaking about he ignition sensor inside the distributor are there two or three wires coming out of it ? I think the original ones had two wires with post connections on the side of the distributor, these were failure prone and replaced with a sealed three wire unit

 

[Ed Harris]

If I have to get a 3 wire sensor where does the 3rd wire hookup? Looking at the new 3 wire it looks as if they added a separate ground wire. Would this be correct?

Ok....I found a diagram of the dizzy
I was thinking this thing still had points in it but I was wrong in my thinking, which tells ya I have never taken the dizzy cap off this unit.
I was going to pull the plugs and have a look and do some compression testing while i had the plugs out. Was also looking at getting a new cap and rotor.

 

[alldodge]

The 3rd wire goes anywhere it can be grounded. Can even use 1 of the 3 screws that hold the body of the electric choke, or anything else that is grounded

 

[Ed Harris]

with there being so many new part numbers out there what is the current part numbers for this engine?
Dist. Cap
Rotor
Sensor

 

[alldodge]

Items 2, 5 and 6
https://www.mercruiserparts.com/bam/subassembly/31770/1939/50

 

[Ed Harris]

Thanks a bunch AD….

 

[dubs283]

The 3rd wire goes anywhere it can be grounded.

Best is to stack it next to the main battery ground on the flywheel cover stud. Thus ensures the best ground possible and why the ring terminal for the ground is 3/8"

Grounding this way is required for efi engines but also recommended for all thunderbolt ignition systems

 

[Ed Harris]

I guess I am going to need more than just a distributor cap and spark plus

 

[Scott06]

View attachment 362436
I guess I am going to need more than just a distributor cap and spark plus

yeah hopefully just a head gasket between 5/7 but could be valves if risers were leaking back into cylinder

 

[Ed Harris]

Yes at a minimum it’s going to be intake and some head gaskets

 

[alldodge]

Suggest;
Pull both heads and look close at cylinder bores. If they look good and there isn't anything that stands out like excessive wear, get a valve job done on both heads

 

[achris]

How Mercruiser Thunderbolt ignition systems work.

Mercruiser Thunderbolt ignition systems. Mercruiser introduced the Thunderbolt IV onto their engines in 1982, alongside the introduction of the 1-R drives. The TB-IV system was used until the introduction of TB-V mid-way through 1996. Thunderbolt V was an improvement on an already exceptionally...

forums.iboats.com

 

[alldodge]

 

[achris]

???

 

[Ed Harris]