2007 Tohatsu 3.5 HP 4 stroke. No spark.

w2much

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Thanks for looking. Is there a way to test the igniter on this motor.. Ignition system is comprised of the flywheel and igniter. I dont have a spare to switch out. I am going to reinstall it today, scraping away some paint to be certain all is grounded. I was thinking there must be an Ohm's test at least but I do not have this manual not did I find the info at CDI or Walbro.
 

w2much

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Thought I would add this as it sure is hot out there today. I put it back in place and realized there should be a certain gap between it and the magnets so I gave it a small one, enough to clear and not rub. It then had spark but did not run real well. As I was trying to adjust the fuel air screw it stalled. Fuel cap was vented, there was fuel to the carb. now if it has a spark it is hard to see becauseit is so sunny out. I will check at dusk. what kind of gap should there be at the magnets and igniter. I realize it could be a heat related electrical failure but not yet ready to throw money at it.
 

pvanv

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Apr 20, 2008
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Assuming you have an MFS3.5A with late ignition or a 3.5B.
On p 8-6 of your Factory service manual, you will see the igniter to flywheel gap specs as .2 to .4 mm, or 8 to 16 thousandths.
Secondary resistance at least 6K ohms. Usually higher.
There is also a diode you can check between brown and black.
I have never had a bad igniter.
 

w2much

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Thank you Paul. I hope I dont have one either. I will do the checks here and post back. Appreciate your reply. .
 

w2much

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Does the distance of the igniter and the flywheel increase and decrease the spark ? I am having a hard time keeping this motor running. I am at the point of turning around again and thinking its a fuel issue.
 

pvanv

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Over 90% of the issues with these are fuel. As long as the igniter is close enough to the flywheel, you will get spark.
 

w2much

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I strongly agree. I was just curious about the igniter distance issue. The orifices on these motors are so tiny they dont have much of a chance of remaining clear unless the motor is maintained well and the owner is aware of what it takes to keep these motors in running condition.. Just my opinion. So the tether switch was going bad and replacing it fixed the spark issue but it still ran terrible, surging, stalling, then running great. Shut down then hard to start. Had the carb off a few times. Cleaned it as well as the fuel lines, flushed the tank, made certain there were no leaks, made sure the fuel on off was working properly. Custumer did not tell me he had gone into the carb and had broken a thin peice of wire inside of the main jet up through the nozzle. It was broken in such a way that you could not see it . I used a jewelers loop and bright light to catch a reflection of it. I tried to grab it and pull it out, wasted time on that method.Finallly blew it out under high pressure. Motor runs great now. Another problem solved thanks to the IBOATS forums and its expert advice.. Thank you .
 
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