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Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 14292
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Ok 1990 stingray with a mercruser 5.0 305. Was starting a

Customer Question

Ok 1990 stingray with a mercruser 5.0 305 . Was starting a few days ago but back firing at fast accelerate , I asked Jason on this sight for help . Drained gas did tune up plugs .035 rotor ,cap . Did notice when I removed coil wire there was oil there swapped with my chevelle coil .also changed fuel filter. Now it won't start at all .note thunderbolt ign. Seem I have no spark . Any help please getting very frustrated
Submitted: 4 months ago.
Category: Boat
Expert:  Jason replied 4 months ago.

Hello Jason here,

Auto coils and marine coils are not always internchangable. That being said, disconnect the gray wire at the coil and let me know if spark returns or not.

Customer: replied 4 months ago.
I have put the merc back in since it did start the other day with it
Customer: replied 4 months ago.
There are two take both off
Expert:  Jason replied 4 months ago.

Remove them both

Customer: replied 4 months ago.
Took both gray wires off still won't start, could it be the thunderbolt device or the magnetic pick up in distributor
Expert:  Jason replied 4 months ago.

Could be... We'll go step by step to figure it out.

What does the voltage read on the purple wire on the coil with the engine cranking over?

Customer: replied 4 months ago.
7.8
Expert:  Jason replied 4 months ago.

Okay that's a little low. Get some scrap wire and make up a jumper wire with alligator clips on each end. Clip one end to battery positive, clip the other end to coil positive. This will bring the coils voltage closer to 12. Let me know if it starts with the jumper in place.

Customer: replied 4 months ago.
Should I reconnect gray wires
Expert:  Jason replied 4 months ago.

No, leave them off for now

Customer: replied 4 months ago.
Ok still won't start now have 9.8 volts
Expert:  Jason replied 4 months ago.

What is the voltage at the battery reading with the engine cranking over?

Customer: replied 4 months ago.
10.4 volts
Expert:  Jason replied 4 months ago.

Is this thunderbolt 4 or thunderbolt 5?

Customer: replied 4 months ago.
Thunderbolt 4
Expert:  Jason replied 4 months ago.
I'm uploading the troubleshooting flowchart for this system, it will cover how to test the rest of it. Give it a read and let me know how you make out.
Customer: replied 4 months ago.
I'll try
Expert:  Jason replied 4 months ago.

Okay let me know what happens.

Expert:  Jason replied 4 months ago.

Please do not forget to come back and rate my help if you end up getting it figured out.

Thanks again and good luck!

Jason

Expert:  Jason replied 4 months ago.

Any progress?

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