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b88 25hp no spark #2

J

jake2250

New member
"Went fishing and motor starte

"Went fishing and motor started to idle rough, checked and have no spark from the #2 cylinder?
Replaced coil, still no spark?"
 
"Replaced the coil or swapped

"Replaced the coil or swapped the coil? (just asking in case you put in another coil that may or may not work).

If you are sure the coil is good, plus the lead wire and the plug, then next step is to test the trigger (simple resistance tests are possible)."
 
"Well, I checked voltage at &#

"Well, I checked voltage at + - on the coils and get 19 volts when fired, So I am getting some power to the coil,, How do I check the trigger?
What values am I looking for.
Also this morning, My timming light picts up firing at the top most portion of the #2 wire, But nothing at the plug. swapped plug wires,, still the same? scratching my head?????"
 
"To test the trigger, disconne

"To test the trigger, disconnect the two trigger leads at the switch box and test across the two leads for resistance (it doesn't matter which probe in on which wire).

At a Rx100 setting you are looking for 6.5-8.5 ohms of resistance (or nearly complete continuity).

It's worth testing, however, from what you describe now, it sounds like you have an issue with your switchbox. It is basically a rectifier (to convert the stator's AC to DC) and capacitors to store the energy for release to the coils (when signaled by the trigger).

Your situation appears that the switchbox is providing insuffient power to your number 2 coil for proper spark.

However, do test the trigger, since that could also potentially be the issue. There is no way to really test the switchbox other than eliminating other ignition components as the source of the problem..."
 
"due as Graham says, and check

"due as Graham says, and check the voltage going to the other coil to compare to the bad cyl. You also checked the plug right."
 
"Ok,, I have attached some pic

"Ok,, I have attached some picts, Just want to be talking about the same thing.
Thanks for the help..
116381.jpg
Switchbox??"">
116382.jpg
Trigger??
 
"Yes, checked plugs, switched

"Yes, checked plugs, switched them,good, I also replaced ground wires to confirm good ground. Replaced #2 spark plug wire also to check, switched this with #1 to confirm good.
116385.jpg
coils
 
"JB, yes I compared voltage to

"JB, yes I compared voltage to #1 coil, jumps to 19v, when fired, I also switched coils back and forth to confirm #2 was an issue.
Thanks for your help,, Electrical issues are a head scratcher!!"
 
"Ok, checked the b/w + the

"Ok, checked the b/w + the b/y from the input side and came up with 7 ohms. Checked from the out put side and got nothing..
116389.jpg
b/w + b/y."">
116390.jpg
7 +/- ohms
 
"Well, I followed a list of ch

"Well, I followed a list of checks,, Switch box wires,First I disconnected the green/white and the green/yellow from the coils.
Green- Black/yellow+ = continuity.
Black/Yellow- Green+ = No continuity.
Geen- Groung pin+ =550ohms
Ground pin- Green+ = no continuity
Ground pin- spark plug terminal+ = #1=700ohms
#2=1000ohms
I left the coils grounded.
Thanks
Bob"
 
"Thanks JB, I'll run this

"Thanks JB, I'll run this series of test again, Everything checks out normal with the exception of the new coil is 200 ohms lower.
I purchased another coil and will start process of elimination from spark plugs back,, Trigger and Stator check out ok so I suspect switch box, although I will spend the smaller amount of cash first before I drop the money on a switch box...
Thanks for listening and helping.
Bob"
 
"for your info, the second pic

"for your info, the second picture in post 7 is the rectifier, it changes a/c voltage to d/c to charge the battery(red wire) and run a tach(grey wire). The link I gave you also has parts break down. The trigger is under the flywheel and attached to the base/linkage, it moves to change the timing above say 1/2 throttle. It can be tested without removal but the flywheel must be removed for replacement. You can also access the stator once the flywheel is removed."
 
"Bob, sounds/looks like you ha

"Bob, sounds/looks like you have done all the tests correctly, and do agree that a second check is well worth while, but believe that you are also correct in suspecting the switchbox.

I have found these to be quite durable (like the rest of the ignition on small Merc's) and rarely fail, but it does happen.

But yes, with a switchbox (new) running anywhere between 150-200 bucks, definately eliminate everything else first..."
 
"Bob,

It has to be the swit

"Bob,

It has to be the switchbox, it can't be the trigger. The trigger has only one coil.

Tony"
 
"Update: Just recieved a new O

"Update: Just recieved a new OEM swithchbox from this site, installed in less than five minutes....
Motor runs GREAT!!! That was it!! Thanks For ALL the help on this!!
This forum is great!!
Graham,JB, and Tony, Thank You!
Bob"
 
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