How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Jason Your Own Question

Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 9282
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
Type Your Boat Question Here...
Jason is online now
A new question is answered every 9 seconds

I have a 2004 90 hp yamaha 2 stroke. I just changed the plugs

Resolved Question:

I have a 2004 90 hp yamaha 2 stroke. I just changed the plugs on it and it runs great, but it will not shut off. I have pulled the lanyard on the kill switch and it still runs. When I cut the switch off the power to the gauges cuts off but not the motor.. Any thoughts? The motot is on a 04 Alumacraft boat. Thanks
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.

My name is XXXXX XXXXX X will be helping you today. Most questions will involve troubleshooting, and usually take many posts back and forth.

 

Is the engine running right now as we speak?

Customer: replied 2 years ago.
No, It is hanging in the slip and I just tried it again about an hour ago, same issue.
Expert:  Jason replied 2 years ago.

Gotcha,

 

This engine uses a CDI ignition system. The problem can be one of a few things, and in order to figure it out you have to know how a CDI Ingition system works.

 

In a nutshell here is how a CDI iginition system works. CDI means capacitor discharge ignition.

 

The main components of the system are the flywheel, the stator coil, the pulser coil(also known as a trigger coil), the CDI box, and the ignition coil.

 

As the engine spins, magnets inside of the flywheel sweep past the stator coil and generate electricity. It makes anywhere from 100 to 300 volts AC. That AC gets sent down to the CDI box, where it is changed over to DC (rectified) and stored inside of a capacitor inside of the CDI box. After that cycle happens. The flywheel magnets sweep the pulser coil, and generates a small amount of electricty, anywhere from a 1/2 volt on up. That "pulse/trigger" signal then travels down to the CDI box. It activates a SCR inside of the CDI. A SCR is a silicon controled rectifier, it is basically a little switch. When the SCR gets the signal from the pulser, it allows the stored voltage inside of the capacitor to leave the CDI, and travel down to the ignition coil. All an ignition coil is, is a step up transformer. It takes the 100+ volts it gets from the CDI and steps it up to the 20K + volts needed to fire the spark plug. And then the cycle repeats itself over and over. Many thousands of times a minute. For every 1 rpm of the engine, the igntion system cycles as I described.

 

Now when a CDI igntion system is running (the engine is running) what happens when you want to turn it off is that you are grounding the stator voltage that runs into the CDI box. This is called the stop circuit. On the Yamaha, there is a white wire that runs out of the CDI box, and goes into the main harness. Up at the front of the boat, that white wire splits off to 2 locations. It runs to the emergecy stop switch, and it runs to the keyswitch. If you pull the emergency stop switch, or turn the key off, you are grounding that wire wire, shorting the CDI box, and stopping the engine.

 

What you want to do first is locate the white wire comming out of the CDI and first simply see if it has become disconnected from the rest of the harness. If it has, plug it back in and try it. If the wire is plugged in, what you want to do is unplug it, start the engine, and then take that white wire and jump it to ground. The engine should stop. If it does not stop, the CDI box is bad.

 

If the engine does stop, then the problem is 1 of 2 things. The white wire has a break in it someplace in the harness, or, ground is missing up front where the wiring for the keyswitch and emergency stop switch is.

 

That should get you going, and hopefully lead you to why its not shutting off. Now that you understand how it works, you should be able to find it if your just a little handy with electricity. 1 thing you want to watch out for is when the engine is running, there will be 100+ volts on that white wire. You want to be careful not to touch the bare wire. Touch the insulated portion of the wire or use plastic electrical pliers to move things around if you are not comfortable with electricity. There is not enough amperage on the wire to kill you. But there is enough voltage on it to give you a nasty shock.

 

Post back with any questions

Regards,

Jason

Customer: replied 2 years ago.
Perfect. I appreciate the help.
Expert:  Jason replied 2 years ago.

Your very welcome. Please do not forget to hit the accept button on your end if you found this helpful. You can still post back afterwards if you need to.

 

Good luck!

Jason

Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 9282
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
Jason and other Boat Specialists are ready to help you

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
< Last | Next >
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
  • He answered my question promptly and gave me accurate, detailed information. If all of your experts are half as good, you have a great thing going here. Diane Dallas, TX
 
 
 

Meet The Experts:

 
 
 
  • Dominick

    Marine Mechanic

    Satisfied Customers:

    1009
    25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
< Last | Next >
  • http://ww2.justanswer.com/uploads/dominickb/2008-12-14_204035_dominick.jpg Dominick's Avatar

    Dominick

    Marine Mechanic

    Satisfied Customers:

    1009
    25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
  • http://ww2.justanswer.com/uploads/TE/TedG/2012-6-15_14759_avaLarge.64x64.jpg Ted G.'s Avatar

    Ted G.

    Rigger, Diagnostician

    Satisfied Customers:

    557
    40 years boating, Safe boating instruct., Offshore Race promoter, Failure Analysis, Expert Witness
  • http://ww2.justanswer.com/uploads/whitesmarine/2009-11-07_025719_07011.JPG John White's Avatar

    John White

    Marine Mechanic

    Satisfied Customers:

    306
    11 years experience working on outboards, inboards, sterndrives & pwcs
  • http://ww2.justanswer.com/uploads/OL/oldnewenglandmarine/2012-9-8_15014_icon.64x64.jpg Jason's Avatar

    Jason

    Marine Mechanic

    Satisfied Customers:

    7718
    Degree in Marine Technology. Gas and diesel marine mechanic.
  • http://ww2.justanswer.com/uploads/JA/jacksparrow1956/2011-1-16_191846_009.64x64.JPG Tan's Avatar

    Tan

    MerCruiser Certified Technician

    Satisfied Customers:

    7330
    39 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
  • http://ww2.justanswer.com/uploads/JE/JeffGr/2012-6-15_14217_20001003AA1.64x64.JPG Jeff G.'s Avatar

    Jeff G.

    Marine Mechanic

    Satisfied Customers:

    4172
    39 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
  • http://ww2.justanswer.com/uploads/dkreines/2008-3-22_155128_daveja.jpg Captain Dave's Avatar

    Captain Dave

    Marine Mechanic

    Satisfied Customers:

    2672
    USCG Licensed Captain, 20+ Years Boating, Fishing, Maintenance and Repair Experience