How to Check Spark and timing affects

[boomboom]

I think i have a two part question

Johnson 70hp 1991 J70TLEIE

I have been checking my spark and everything i read is " bright blue thick spark" at 7/16 gap. Maybe im looking for a little more discription of good spark? Im seeing thick spark from one end of the tester, thinner spark coming from the other side so you can see a skinny spot almost in the middle where they meet. As i turn the key the rythm looks good but it misses one every once in awhile. Is this normal or am i looking at it too much and sniffing too many fumes?

Also when checking the timing i noticed the time light "misses" every once in a while. I even moved the time clamp to the other two wires to just watch the light. Cant tell if it coincides with the miss in the spark but i kinda see the same thing when checking the spark.

Idle time is supposed to be 3-5 atdc when i checked it we were running 4 btdc. Didnt catch the a or b till after i put the boat away.

Engine has a slight miss at idle that is making me pull my hair out.

thanks in advance!

 

[boomboom]

Re: How to Check Spark and timing affects

I just read a noticed something. Is timing supposed to start to advance just before throttle plates open? My plates are 1/4 to 1/2 open before spark advances. The timing lever has a spring on the back side so the lever moves and takes up the slack before the time came starts to move. I kinda think the spring needs to be on the other side ie between time lever and time cam.

By the way my oem manual will be in tuesday but it bugging me

 

[tashasdaddy]

Re: How to Check Spark and timing affects

correct timng procedure. http://forums.iboats.com/showthread.php?t=228183

wait for you manual, before you screw up.

 

[F_R]

Re: How to Check Spark and timing affects

I just read a noticed something. Is timing supposed to start to advance just before throttle plates open? My plates are 1/4 to 1/2 open before spark advances. The timing lever has a spring on the back side so the lever moves and takes up the slack before the time came starts to move. I kinda think the spring needs to be on the other side ie between time lever and time cam.

By the way my oem manual will be in tuesday but it bugging me

It is messed up. At slow idle, the throttle plates should be closed and the RPM is controlled by spark advance/retard. As you slowly advance the throttle control, the spark advances, till at the proper moment, the cam touches the throttle plates roller. Continued movement will continue to advance the spark and slowly open the plates. Once you reach full spark advance, the throttle plates will be open perhaps 1/4. Then, continued control movement will rapidly open the plates fully, without moving the spark any more.

EDIT: And don't get all hung up on that thick blue spark thing. In fact, don't even think about it. If it is sparking 7/16" it is fine. However, missing sparks is another matter.

 

[boomboom]

Re: How to Check Spark and timing affects

I will wait for the book before I play with it too much more. Sounds like I need get the spark advance going slot earlier. I'm convinced there is something wrong with the little plastic rod coming off the time cam. In idle the sleeve sits at the far left of the platic rod, as I increase throttle that sleeve has to move bout 2.5 inches to the right before it makes contact with the other end of platic rod and moves time cam. Seems like I'm missing a stop on this platic rod maybe? I do think the spring is on the correct side , left of the sleeve.

 

[boomboom]

Re: How to Check Spark and timing affects

alright

i ended up getting 3 spark gap testers and checking spark all at once. I think i was chasing a bad ground with the tester before. I changed the number three coil as it could not jump the 1/2in gap. Runs better but its not there yet. I have now done the link and sync per oem manual.

I am still struggling with getting the timing cam to advance before the throtle cam moves. I kinda dont think its supposed to. I will post a picture soon to further explain. If i lower the idle time to 4atdc it wont idle in the water. Does fine on the muffs though.

 

[boomboom]

Re: How to Check Spark and timing affects

Here is a picture straight from my oem manual. Notice the roller just above the throttle cam mark, this is the point where time cam has slid to the right releiving the spring tension and starting to advance timing. Unless im missing something the throttle has to open just a tad prior to advancing time. The only way i have been able to do it is leave a 1/2inch gap between the throttle cam and the roller, which is not spec.

All this said i still think my problem lies with intermitent spark loss. I see it on all cylinders. When doing spark gap test you can see it miss a spark occasionally. Can my stator have a dead spot on it????

 

[boomboom]

Re: How to Check Spark and timing affects

So i finally am getting somewhere with the boats idleing problem. I beleive i had an air pocket in side the fuel water separator. Its the moeler type looks like and oil filter. With the clear tubing in the fuel line trick i always had an air bubble. When i pulled the line off the motor and pumped the bulb i had 2 good pumps then nothing for 7 or 8pumps. I guess i never primed the filter cause after that i had no air bubbles. Now it starts like a champ when cold and starts without choke after fishing for an hour!!!

Time is still advanced quite a bit at idle but its reliable now and thats what matters. Would still like to bring the time back to spec as the time cam screw is pretty much all the way in and if i back it out at all it dies quick.