25 HP Mercury no spark.

[kory kreisler]

Hello,
I have what I beileve is a 87-88 25 hp Mercury outboard that had been sitting for the past few years, ran when I parked it, no spark last night when I tried to start it. I don't see any chewed wires and checked to make sure the "kill switch" was in the run position but that's as far as I got. Goint into this I thought I may have to clean the carb, but didn't expect electrical issues after sitting.

From what I have read it could be the stator, switch box, coils etc. What I am wondering is what item is most likely to fail in a condition of non use? Where should I start first to identify the problem?

Any help would be appreicated!
Kory

 

[jfishn]

Re: 25 HP Mercury no spark.

I'm no professional mechanic but I think there are only a few things that control fire on both cylinders. ONe would be the neutral safety switch, another would be the kill switch, and lastly the switch box?

Is it electric start or manual?

Because the switch box is sealed for the most part I'm guessing it last as the problem. The kill switch if it's on controls would be my first choice, followed by a neutral safety switch (if electric start)?

Good Luck..... There are several good Merc guys on here so you should get some info...

 

[kory kreisler]

Re: 25 HP Mercury no spark.

I did some more troubleshooting last night.

1) I disconnected the Black/Yellow wire from the harness to the switch box to override the Kill Switch and still no spark. Would this eliminate the kill switch and the neutral safety switch?

2) I checked the OHM readings for the stator and the trigger and they were both about 5% lower than the CDI Test instructions listed on a different post. Could the lower OHM readings be the problem? I would think that they would result in a weak spark vs no spark at all.

3) Took off the flywheel and ensured that there wasn't any obstructions, found 2 ladybugs but that didn't change anything.

4) Started wondering, if the key was put into the run position unitl the battery was dead, could it overheat the switch box and cause failure??? I don't remember what position the key was in when I got the boat but the battery was dead and the cover was half off maybe some kids got in there and were messin around....

Should I assume that it is the switch box and bite the bullet and order one or could it be something so simple that I just don't see it?

Jfishin,
It's an electric start, but it does have a pull rope also.

 

[kory kreisler]

Re: 25 HP Mercury no spark.

Well I went out to the garage and got the actual readings of the trigger and stator hoping that someone can help me out a bit.

Stator: LS, Black/Yellow to Ground = 2860 ohms
Stator: HS, Black White to Ground = 130 ohms
Trigger: Brown/Yellow to Brown White = 708 Ohms

ALL of the readings are lower than should be expected but is this enough to cause a complete lack of spark?

 

[Laddies]

Re: 25 HP Mercury no spark.

While the trigger ohm,s are a little low the others are in the ball park and I doubt if the low reading is anything more than a temperature flux. Without a DVA to give a output reading it's hard to say for sure but it does sound like a bad box.

 

[kory kreisler]

Re: 25 HP Mercury no spark.

Thanks Laddies, I ordered the switch box and hopefully it does the trick, I let you all know how it turns out. I figured it was the box before I did any tests, Murphy's Law and me get along pretty well. So when I found out it was the most expensive part to replace..... well you know.

Cheers,
Kory

 

[kory kreisler]

Re: 25 HP Mercury no spark.

Got the switch box today and it solved the problem! Hopefully it wasn't another part that caused the switch box to go bad.. time will tell.

Thanks again,
Kory