# Mercury 15HP outboard



## kbkid

Some of you may have seen my thread regarding my recent purchase of a 14 foot Sears jon boat with a 15HP Mercury motor. When I bought the boat, the previous owner was about to start the engine on about the second or third pull of the starter rope. He did this on three separate occasions, so I felt the engine was fairly reliable.

Today, only three days after the engine was last started, I have been unable to get it running since getting it home. I've followed the instructions the previous owner gave me as well as looking at the manual he provided. 

1. Flip engine to RUN.
2. Prime engine by squeezing fuel line pump. 
3. Rotate choke knob clockwise and pull knob out.
4. Pull until tension in starter rope, then pull starter.

After following those instructions, I have yet to get anywhere. The fuel tank has new fuel with the proper 50:1 ratio. The fuel lines are not clogged because fuel is getting to the carburetor. Fuel is also getting to the spark plugs.

I believe I've narrowed it down to the plugs not getting a spark. I've replaced the plugs and still nothing. So now I come you guys, seeking help in trouble shooting this problem. Where do I begin when the plugs are not getting spark?

Sorry for the long post, I just wanted to make sure everything is out on the table and everyone knows the situation.


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## kbkid

In case it helps, the only number I have found on the motor is a serial number listed as 0B319929.


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## crazymanme2

You probably have the kill button activated or make sure the kill button is not faulty.Should be able to test with an ohm tester.If its truly an electrical problem Mercs are not the easiest to trouble shoot.Keep us posted
.


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## kbkid

The vent cap was open on the fuel tank. I'm unsure about the kill switch. If I took another picture of the front of the engine, would that help in locating such switch?


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## taxidermist

Well check the spark even buy setting the plug to wehre you can see the spark in the plug.

If it ran before its the kill button they are bad for shorting out, 10 bucks at most Merc dealers. You can unhook the kill button and check it.

When you sqeezed the bulb did the bulb get firm? if not then not enough priming.


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## Zum

Are you sure it's not getting spark?
You may have flooded it by now.?
Does it try to start or nothing?
It would be pretty hard luck if the kill switch just went,3 days after purchase...not saying impossible but hard luck.
Is there 2 kill switches by chance?
Maybe a wire came off if transport?


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## kbkid

The motor ran on Thursday, on about the third pull.

Are you guys referring to the RUN/STOP switch when talking about the kill switch? Is there anyway to check the switch with a multimeter to see if it is working properly?

Also, I've searched online for a manual of some sort for this motor. Everywhere I look asks for a model number but all I can find is a serial number.


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## kbkid

I pulled the plugs out and cleared the motor of any fuel by pulling the starter rope. I also left the plugs out for a good hour or two in hopes of any fuel inside would evaporate. Initially I may have flooded it, but it shouldn't be any longer.

When I pulled the plugs out, I grounded them to the engine block while someone else tried starting it. No spark was seen. Therefore I don't think the spark is making it this far. 

The motor turns over, just does not start. 

Now regards to there being two kill switches, I have no idea. The previous owner only mentioned one switch. He was able to start it by turning it to RUN and choking it.


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## Zum

Your right shouldn't be flooded.
Man,does sound like it may be a bad switch,just hard luck though.
I doubt it but do you have one of those emergency clips,that hold the outboard in the run position?

With your outboard in run position,1 side of your switch should be to ground and the other wire should go to ignition.With multi meter(ohms)take black lead put on ground.Take red lead,put by ignition or the wire that goes to it,,,should be infinite or open.Push killswitch or remove emergency clip and should show a low reading or short.

It's easier to do it, then for me to try to explain it...
Maybe someone else will have a better explanation.

Still find it hard luck,3 days ago worked...


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## kbkid

I pulled the cover off and took the switch out.

When doing so, I can see that the two wires going to the harness that connects to the switch are frayed. There is a good bit of gunk of some sort in the bottom of the engine cover. I did my best to clean it up and I was able to isolate the two wires.






The thing is though, I think this is just another problem on top of the plugs not getting spark. I don't think those two wires is the cause for all this trouble.

And yes it does appear as though my luck is pretty bad. I just try to think that some people have it worse than me though.


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## kbkid

As for the motor having the emergency clip, I'm pretty sure it doesn't.

I'm about to go back out and try to test the switch though.


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## crazymanme2

All the switch does is ground the motor out.Put your tester on the 2 wires.(one lead of tester to one wire & the other to the other)when you push button there should be continuity when you let off there should be none.Simple test.Make sure when test for spark that plugs are grounded out.If they are not that is a good way to fry your switch box.


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## kbkid

The way the switch is made, a wiring harness plugs into the back of it. I am unable to put the tester on the two wires unless I unhook the harness from the switch. 

As for the spark plug test, I did have the plugs grounded when attempting to see a spark.


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## Loggerhead Mike

i will bet those 2 wires are you problem

electricity travels the easyest path it can find. If by chance those wires are not grounding out, the broken strands can be enough resistance to open the circuit

you need to cut those wires and soldier new wires on it w/ heat shrink

for kicks and giggles after you cut the wires hook them together. bet she starts rite up

after you fix it find out what is fraying those wires. you need to move them or add some sort of conduit or they will just get frayed again


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## kbkid

The switch appears to be working correctly and I was able to fix the frayed wires. I've followed the problem all the way back to the switchbox assembly. From there, I am stuck.


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## jasonr95

mine wont start if in gear,and have cranked my guts out prove it .


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## kbkid

The tiller handle has been in the neutral position.

Is there anything I can check regarding the magneto operating correctly? Is there a test of some sort?


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## crazymanme2

Loggerhead Mike,I believe that switch is a normaly open switch which when pushed makes contact between the 2 wires & grounds the motor out which is no spark.If he connects the 2 wires together he will have no spark.That is how the kill button works on all 3 of my Mercs.


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## kbkid

After looking at the switch and seeing how it operates, I agree with you completely crazymanme2. 

This is beginning to get a bit frustrating, considering I've only had it for a few days. Does anyone have any other suggestions?


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## CarlF

> Does anyone have any other suggestions?



Sometimes you just have to bite the bullet and take it to a pro!


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## Loggerhead Mike

> If he connects the 2 wires together he will have no spark.That is how the kill button works on all 3 of my Mercs.



sorry fellers i was typin faster than i can think

if your not getting spark you need to start back probing. 

take your plug out and hook the pos lead of your meter to the end of the plug wire and the neg lead to the engine block. have a buddy turn the motor over. any voltage?

if not unplug the wire from the coil and do the same. if nothing ohm the coil out. whats your reading?


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## kbkid

I'll try this when I get home from work.

Take the plug out, hook positive to spark plug cable and negative to engine block. Try turning engine over and get the voltage reading. Correct?

I'll report back later.


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## Loggerhead Mike

yah man. if you dont get anything disconnect the plug wire at the coil and see if your getting any V there.

if still nothing ohm your coil and get back to us


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## alumacraftjoe

Have a 92 evinrude and my wasn't getting spark and it was a bad kill switch. disconnected it and it fired right up.


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## kbkid

After doing some testing, I am positive the kill switch works properly.

I used a Spark Plug tester to eliminate the possibility of the spark plug being no good. Even with a new plug, I was still getting no spark.

I used a Fluke 87 DVM to measure the voltage at the switchbox. The voltage registered just a tad above 3V. 

Granted the electronics on this motor are nearly 21 years old, is there a possibility the switchbox could go bad.


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## crazymanme2

Of the Mercs that I own I have had 1 switch box bad & 1 trigger.Mercs are hard to trouble shoot electrical.Even if part test good it still could be bad.(almost a direct quote from a Merc shop manual)


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## kbkid

Where I should trouble shoot from here? I'm hesitant to order a new switch box, because they go for a little over $100.


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## kbkid

Last weekend though I had the opportunity to mess with the motor some more. I was finally able to get her started, but let me tell you the story behind it.

August 22nd was when I began having problems with the motor. That night, it had rained pretty hard and the next morning there was very dense fog that came over us. I didn't think much of it then, but I remember taking the cover off the motor when it wouldn't start and the entire engine was covered in condensation. I figured since it was a marine motor, it has probably been wet before. So I came to you guys in hopes of figuring out why it wouldn't start.

After putting a multimeter on everything you guys were telling me to, I was still hesitant to buy a new switch box. I ended up going away to college and for two weeks I left it in my garage back home with the cover off and spark plugs pulled. I kept thinking that maybe the condensation I had seen weeks before had caused the problems. This was going to be my last attempt before buying a new switch box. 

I'm still unsure whether the condensation caused the problem or not, but I know everything in the engine should have been pretty dry after two weeks. I pulled the boat out and primered the engine just as I had in the past and the engine fired up on the second pull. I couldn't believe it and I am still in shock and disbelief. 

I just want to thank you guys for the help and check out my build log once I post it later.


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## huntinfool

Glad to hear you finally got her running.


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