Is it the switch box?

[babatten]

Hi guys, i'm new to this forum but have been watching for a while and learned alot of valuable information. My question for you mechanically inclined boaters is what is causing my motor to not run. The motor is a 1996 Mariner 15hp manual start.

Here is what I know so far:

- the fuel is getting through the carb just as it should and everything looks good on that.
- i'm no mechanic but just in pulling the cord or turning the prop the motor seems to have good compression.
- I replaced the plugs and it still wouldn't fire so I pulled the plugs and did a spark test to which it revealed i have no spark from either of my plugs.
- I checked the kill switch and all seems fine there so I am now stumped as I don't deal with electronics much.

I was told that the switch box is a common problem and that I may have to replace that. Could this be the only possibility or is there something else I can check before ordering a $150 part for a $500 motor?

Any suggestions are greatly appreciated.

 

[crem1]

Re: Is it the switch box?

Check out the switch box...see if it is the problem

 

[babatten]

Re: Is it the switch box?

How do I do that? Can I unbolt it and pull it apart to inspect for faulty wiring? Will it be obvious if the switchbox is bad?

 

[narvlebenoit]

Re: Is it the switch box?

It maybe the coils that are bad .

 

[babatten]

Re: Is it the switch box?

I thought the same thing but is it reasonable that both coils went out at the same time?

 

[achris]

Re: Is it the switch box?

It maybe the coils that are bad .

Both coils???? Me thinks unlikely.

A common problem with these engine is the stop switch in the tiller handle shorting to ground. When you said you 'checked the kill switch' exactly how? Trace the wire back to the switch box, you should find that it joins another wire (from the switch in the tiller). Follow it back to the switchbox, and disconnect the bullet connector. That way you know you have completely isolated the kill switches. Now check for spark.

Chris.......

 

[babatten]

Re: Is it the switch box?

You know I saw where the two wires joined together but I never thought to check that. I'll give that a try when I get off work and see if I can't get a spark, but if that isn't the problem then it is more than likely the switch box....correct?

Sorry for so many questions just never had to deal with this particular problem so its a learning experience for me. Thanks for all the suggestions and help so far.

 

[j_martin]

Re: Is it the switch box?

The only real dumb question is the one that's not asked.

 

[babatten]

Re: Is it the switch box?

this is true....I have learned alot about outboards in the past few months and I get great satisfaction from doing the work myself.

I tried disconnecting the kill switches then doing a spark test and it still gives me nothing so without a DVA meter I just have to assume it is the switch box. I'll order one this week and hope that solves the problem.

 

[achris]

Re: Is it the switch box?

Without a DVA meter, if you have a standard multimeter, I would do a continuity check on the stator winding and the trigger winding.

You're looking for about 750ohms on the stator (brown/white and brown/yellow wires), disconnected from the switchbox, with no connection to ground.

About 400 ohms on the trigger (white/green and green/white), disconnected from the switchbox, with no connection to ground.

If they show good, then you have a good chance of fixing it with a new switchbox. Part number for switchbox is -855713A4. They sell them on this site, and cheaper than I've seen elsewhere ....

Chris........

 

[babatten]

Re: Is it the switch box?

I got a multimeter yesterday and tried it this morning. I got a good reading from the two brown wires but I don't see any green wires other than the two coming out of the switch box itself that connect to the ignition coils. The only other wires I see that are coming from under the flywheel area are both black. I tested these wires and got a reading but it was kinda funky and incosistent at best. I don't know if I did this right or not as I have never dealt with it before but I gave it a try.

Any idea if the two black wires I mentioned are the correct ones to test and if so shouldn't they be a little more consistent in reading? If this is the problem is it the stator or the trigger that I need to look into?

I removed the switchbox and all the ground wires so that shouldn't have affected anything but in the process I scuffed the switchbox up. A valuable lesson was learned there about patients when working on your own stuff.

 

[achris]

Re: Is it the switch box?

Your engine has a slightly different stator to mine, so the colours are different, sorry...

See how you go with those.

Chris............

 

[babatten]

Re: Is it the switch box?

Okay thanks, that had me a little confused at first but I think i'm straight now. I ran the diode test like I mentioned before the black/yellow and black/white wires would give me a high number on the meter then go blank until I played with it some more and it would then come up with a totally different number. Its pretty late here but when I get up in the morning I will test it one more time and see how it does. I sure hope I can get this figured out soon cause i'm itching to get it back out on the water.

 

[babatten]

Re: Is it the switch box?

Hey Chris, I looked up the part number you gave me and the picture is of a different box than what I have on my motor. Is the pic just a display for all switchboxes or is this a different box than I need?

My box looks like this: http://www.usboatsupply.com/Mercury_Mercruiser_Parts_Catalog3a.php?mc=02&ms=1480&si=497

Thanks,
Brad

 

[achris]

Re: Is it the switch box?

Brad,

Sorry about the wrong part number... Your box is 339-7452A19.

That year was a change-over year, could have gone either way, and I went the wrong way. :redface::redface::redface:

If you post up your serial number it would get us on the right track....

Do you have the service manual?

Chris.........

 

[babatten]

Re: Is it the switch box?

I don't have a owners manual but the serial # is 0G308968 and it is a 1996 15M. Hope that helps.

 

[babatten]

Re: Is it the switch box?

here's an actual pic of my switchbox, the tape is just for reference as to where to put the wires when I put it back on the motor.

 

[achris]

Re: Is it the switch box?

OK... we're on the same page now....

:redface::redface: That's the box I thought it wasn't. :redface::redface:

Serial number clears it up too....

Chris......
P.S. Nice tool set...

 

[babatten]

Re: Is it the switch box?

Well thats good news cause the switch box that I need is a little cheaper than the other one. Thanks for all your help Chris, hopefully i'll get back out on the water soon!