Mercruiser has no spark but cranks good.

[WSR]

I am a long time user first time poster because of all of the great help I have received over the years. Thank you Don S as well, you are a true saint. All of my issues have been solved by reading, after much research I am now stuck.
I have a 4.3L V6 Mercruiser alpha-one in a 1990 Bayliner Capri with Thunderbolt IV ignition.
I am not getting a spark, however the engine cranks just great. It runs like butter once started.
I had it out two weeks ago and upon launch had a hard time starting, after running for a while (close to the doc) I turned it off. It took a while to start but it did.Went home to flush...hard time again but it fired.
Now on the hose it wont start. I Bought a new coil because it looked original and possibly compromised (The same thing happened on my old VW) still no go. The distributor looks great, clean, spins, points are good, no cracks. I tested the spark plug cables and the are good.
With the key in the "On" position I do not get any voltage on the purple wire at the coil. Should I? I traced the purple everywhere and no voltage. Should the purple have voltage out of the alternator? It seems like no power to the coil is the issue.
I have the SILOCK shop manual and Bayliner owners manual. Please Help.

 

[Haut Medoc]

Re: Mercruiser has no spark but cranks good.

Do you have 12V at the "I" terminal on the ignition switch with the key in the 'run' position?......

 

[WSR]

Re: Mercruiser has no spark but cranks good.

Yes I do 12.10 at the I
thanks for your reply

 

[WSR]

Re: Mercruiser has no spark but cranks good.

That is if I tested it correctly.

 

[WSR]

Re: Mercruiser has no spark but cranks good.

Confirmed! 12v at the I "purple wire".

 

[Bondo]

Re: Mercruiser has no spark but cranks good.

Ayuh,...

The "I" terminal of the keyswitch is where the purple wire gets it's Power....

Another place to Look is for corrosion at the Cannon Plug...

 

[WSR]

Re: Mercruiser has no spark but cranks good.

Where can I find that?

 

[WSR]

Re: Mercruiser has no spark but cranks good.

Duh....sorry.A little corrosion.What is the best way to clean it without possible damage?

 

[Bondo]

Re: Mercruiser has no spark but cranks good.

Ayuh,....

It's the Big Black plug in connector, where the motor's wiring meets the boat's wiring.....
Usually mounted on the starboard aft corner of the motor...

edit;
A wirebrush,...

 

[WSR]

Re: Mercruiser has no spark but cranks good.

It seems minimal, too little for a small wire brush so I gave it a little rub with a tooth brush and blew it off with a air compressor.
Should this give me 12v to the purple wire at the coil?

 

[WSR]

Re: Mercruiser has no spark but cranks good.

Still no power to coil after checking the cannon plug.It has a thunderbolt IV ignition, I have the flow chart to trouble shoot as well.Any other ideas?

 

[Don S]

Re: Mercruiser has no spark but cranks good.

Have you checked the emergency kill switch?

 

[WSR]

Re: Mercruiser has no spark but cranks good.

Do you mean the lanyard deadman kill switch at the helm?Or the circut breaker big red button on engine.I tried it in and out.How else could I test it?

 

[WSR]

Re: Mercruiser has no spark but cranks good.

I feel like it could be the slave solonoid next to the circut breaker.Should I have volatage to all wires connected to it?

 

[WSR]

Re: Mercruiser has no spark but cranks good.

On the solenoid next to the circuit breaker (50 on it) with the key on "on", I have voltage to the red purple wires but no to the yellow red.Should this be live?Or only while cranking?

 

[Don S]

Re: Mercruiser has no spark but cranks good.

The lanyard switch at the helm. If the red circuit breaker was bad, you wouldn't have power to the ignition switch. Since you have power to the switch and out the purple wire going to the engine, it has to pass thru the lanyard switch (deadman switch) to get power back to the coil.

 

[WSR]

Re: Mercruiser has no spark but cranks good.

how can i test it or can i jump it?

 

[Don S]

Re: Mercruiser has no spark but cranks good.

You can test it with an ohm meter with power off, or use a volt meter and see if you have power to it and coming out of it. Hard to say what kind of switch or where it's located go give you any accurate info. If you can jump it, jump it. All it is is switch, and it may be turned off, and like any switch it could break.

 

[WSR]

Re: Mercruiser has no spark but cranks good.

I have access to it.gonna test it now.....

 

[WSR]

Re: Mercruiser has no spark but cranks good.

Wow! I think we are close.I did two tests.one with my light up voltage tester and ohm meter.The light barely lights up if I push it on real hard with the laynrd off.As far as current am I supposed to have 12V here?Because it was around 3.5...on the ohm I got o.ooo with the button pushed in....NEW KILL SWITCH???