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1993 4.3L v6 no start

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Lukemarineengine25

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I just bought a sea ray, I think it’s 1993-1995 somewhere around that I’ve been told

This is my first boat so I don’t know much them

It cranks and gets fuel to the carby but does not have spark.

I’m getting 12v to the ignition coil and to the amplifier.

How can I test if I have a bad amplifier ?

What other test should I do?

Thank you
 
Here is the trouble shooting flow diagram.
Note: some of the connections referenced as Bullet connectors may be ring terminals at distributor.

Also Step 1. Disconnect Grey Tach wire from Coil - If tachometer has issues it can cause an issue. NOW RETEST FOR SPARK.

Next, Find the shift interrupter switch on Shift bracket mounted on Drivers side Exhaust elbow (where two shift cables are mounted (DO NOT MESS WITH ANY ADJUSTMENTS). Wires from switch connect at small two terminal Terminal block. Disconnect White with green stripe wire that goes into the engine harness from terminal block to eliminate the interrupter switch causing no spark. Leave wire end floating in the air, It cannot touch engine as it will be grounded and cause lack of spark. NOW RETEST FOR SPARK.

If still no spark. Follow flow diagram attached

Thunderbolt test fow diagram.jpg
 
Correct terms to describe ignition components

Ignition Sensor - Sensor under/inside distributor cap.

Ignition Module-Also known as timing control module- Is either mounted on passenger side exhaust elbow or on Distributor and has many wires going into it.

Ignition Coil Has a + (plus) and a - (minus) The Minus is NOT ground it is only minus.

Shift Interrupter switch- When shifting OUT of gear (ONLY) (forward or reverse) on Alpha out drive boats, Resistance is generated and the Short shift cable will cause the V notch on shift plate to move and make the Interrupter switch close which shorts the ignition/spark to ground. This happens very quickly for a second or two and allows the Clutch dog engagement in lower gear case to disengage. Without this happening it can be impossible to get back to neutral from either forward or reverse
 
Lukemarineengine25 said:
I just bought a sea ray, I think it’s 1993-1995 somewhere around that I’ve been told

This is my first boat so I don’t know much them

It cranks and gets fuel to the carby but does not have spark.

I’m getting 12v to the ignition coil and to the amplifier.

How can I test if I have a bad amplifier ?

What other test should I do?

Thank you
Click to expand...
Look at back (transom) Of boat. There is a serial number in gellcoat. Typically the last two numbers are the year of the boat So it will show 93 or 94, or 95 if it is truly one of those years. Otherwise the ENGINE serial number is the only way to tell for example if the engine was original for the year of boat manufacture or replaced with a newer/older one.

There are differences between 1993 and 1995 components so knowing the exact engine date/serial number is very important!!
 
Last edited:
kghost said:
Here is the trouble shooting flow diagram.
Note: some of the connections referenced as Bullet connectors may be ring terminals at distributor.

Also Step 1. Disconnect Grey Tach wire from Coil - If tachometer has issues it can cause an issue. NOW RETEST FOR SPARK.

Next, Find the shift interrupter switch on Shift bracket mounted on Drivers side Exhaust elbow (where two shift cables are mounted (DO NOT MESS WITH ANY ADJUSTMENTS). Wires from switch connect at small two terminal Terminal block. Disconnect White with green stripe wire that goes into the engine harness from terminal block to eliminate the interrupter switch causing no spark. Leave wire end floating in the air, It cannot touch engine as it will be grounded and cause lack of spark. NOW RETEST FOR SPARK.

If still no spark. Follow flow diagram attached

View attachment 36534
Click to expand...


Thank you so much for your comment, now I have something to work with. Really appreciate it

I disconnected the grey wire at the coil. Still no spark

I then disconnected the shift interrupter switch( red and white wire at the switch). Still no spark

( I have a inline spark tester attached)


I have 12v at the ignition coil (both sides)

I then checked power out of the red/white wire coming out of the module and I had 1v

The flow chart tells me to replace the amplifier
 
kghost said:
Look at back (transom) Of boat. There is a serial number in gellcoat. Typically the last two numbers are the year of the boat So it will show 93 or 94, or 95 if it is truly one of those years. Otherwise the ENGINE serial number is the only way to tell for example if the engine was original for the year of boat manufacture or replaced with a newer/older one.

There are differences between 1993 and 1995 components so knowing the exact engine date/serial number is very important!!
Click to expand...
The boat has been painted so I can’t find any numbers on the transom but my engine serial number is F073076
 
"""
I then disconnected the shift interrupter switch( red and white wire at the switch). Still no spark
( I have a inline spark tester attached)
I have 12v at the ignition coil (both sides)
I then checked power out of the red/white wire coming out of the module and I had 1v
The flow chart tells me to replace the amplifier"""

After detaching tach grey wire and white/green AT interrupter switch- Leave disconnected until testing is completed!!

Attached is what I think is your schematic (with Thunderbolt 5 timing module mounted on distributor (you do not specify).

Problem, Wire going to shift Interrupter switch is WHITE/GREEN NOT White/RED. Double check!!!

Also Did you do the try test 5?
This test simulates the pulse for coil to fire. This will determine if sensor inside dist cap is bad. (spark comes out of center tower or coil wire which ever you choose to insert spark checker)

Also I would suggest pulling connector at timing module and look closely at pins for corrosion or burning..


Screenshot 2025-11-30 073111.jpg
 
kghost said:
"""
I then disconnected the shift interrupter switch( red and white wire at the switch). Still no spark
( I have a inline spark tester attached)
I have 12v at the ignition coil (both sides)
I then checked power out of the red/white wire coming out of the module and I had 1v
The flow chart tells me to replace the amplifier"""

After detaching tach grey wire and white/green AT interrupter switch- Leave disconnected until testing is completed!!

Attached is what I think is your schematic (with Thunderbolt 5 timing module mounted on distributor (you do not specify).

Problem, Wire going to shift Interrupter switch is WHITE/GREEN NOT White/RED. Double check!!!

Also Did you do the try test 5?
This test simulates the pulse for coil to fire. This will determine if sensor inside dist cap is bad. (spark comes out of center tower or coil wire which ever you choose to insert spark checker)

Also I would suggest pulling connector at timing module and look closely at pins for corrosion or burning..


View attachment 36541
Click to expand...
Thank you for your help! I did all of the above and still didn’t start

I just received a second hand amplifier from overseas and installed it

I now have spark.

It started briefly then cut out and seems like it’s about to start but won’t or will for a second

thank you for all your help and getting me this far
 
Lukemarineengine25 said:
The boat has been painted so I can’t find any numbers on the transom but my engine serial number is F073076
Click to expand...
Did you get a title with the boat? The year and serial numbers should be on that. State DNR and Coast Guard will have a field day if your boat isn't registered if you're in the US.
 
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