'03 90hp Merc-NO SPARK!

S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
I have a 90hp Merc on a 17' bowrider. It is put into the water in May and remains there until late September.<br /><br />Motor has maybe 50 hours. I don't have an hour meter but figure I put 150 gallons of gas over the past two seasons. I don't use it alot.<br /><br />Friday evening, wife and I pull away from the dock. Motor had not been run in 4 weeks. Started right up. Sounded normal.<br /><br />Put in reverse and pulled away. Go out to the water(fresh water) and went forward. Could not get above 3K RPM. Thought there may be weeds. No weeds!<br /><br />Go back to dock and pull plugs(new, maybe two hours on them). Top plug shows no sign of firing. Bottow two look normal.<br /><br />Start motor up, pull top plug boot, no spark. Bottom two have spark.<br /><br />Switch coils between number 1 and 2 plug. Now no spark on number two. Spark on number 1.<br /><br />Coil right?<br /><br />Go to dealer Saturday, pick up new coil($70). Put in, no spark still on number 1.<br /><br />Back to dealer, try coil, strong sprark on a 40hp Merc motor.<br /><br />Back to boat, try new coil and original coil, no spark with any coil on whatever plug I try. Use other coils and am fine. Seems like will not fire 3 coils.<br /><br />Any ideas?<br /><br />Motor runs fine. Just no spark on 1 cylinder and no power.<br /><br />Spark seems to be related to the coil (either new or old)and not plug.<br /><br />Any ideas? Got one long weekend left (Labour Day).<br /><br />Tx.<br /><br />Joe
 
D

dakk1

Chief Petty Officer
Joined
Apr 22, 2003
Messages
418
Re: '03 90hp Merc-NO SPARK!

Hmmmm. That's a tough one. Did you check for spark with the plug out?<br /><br />Dave..
 
Dunaruna

Dunaruna

Admiral
Joined
May 2, 2003
Messages
6,027
Re: '03 90hp Merc-NO SPARK!

Are we talking 2 stroke/4 stroke, EFI/carb?????
 
S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
Re: '03 90hp Merc-NO SPARK!

Dave:<br /><br />I didn't check for spark with the plug out. I figured that since I got spark with another coil, plug should be fine.<br /><br />Part I find strange is that the engine sounds normal. Just no power. When I put a different coil on number two and it does not work, it does not run as smoothly. Figure it must be firing order causing the lack of balance.<br /><br />Engine has always run realy well. I'm actually quite upset by the whole thing.<br /><br />Had an evinrude fleet (okay, two motors) and switched to Merc now. I'm both stumped and ticked. It should be the coil but it does not appear to be....<br /><br />Joe
 
S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
Re: '03 90hp Merc-NO SPARK!

Sorry, should have added this. It is a 2003 Mercury 90 HP Classic Two Stroke. <br /><br />Should be pretty straight forward fix. It not the coil, switch box? But it will spark on any 2 cylinders. Just not on three?<br /><br />Joe
 
A

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: '03 90hp Merc-NO SPARK!

Just so I understand. You had no spark on 1 (say #1 for instance) cylinder and spark on the other two. You switched the leads from the switchbox to the coils (i.e. the lead from the switchbox to cylinder 1 is now on cylinder 2. And the lead from the switchbox to cylinder 2 is now on cylinder 1). Or plainly, the "no spark" jumped from one cylinder to the next. If this is what happened, then it is your switchbox.<br /><br />The fact that you got the coil that wasn't firing to fire by switching leads would tell you that it isn't bad.<br /><br />If this isn't what you were saying...Explain again.<br /><br />-andy
 
S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
Re: '03 90hp Merc-NO SPARK!

I switched the coil from cyl 1 to cyl 2. This switch inludes both the leads from the wiring harness to coil and high tension lead to spark plug.<br /><br />Essentially moved coil 1 to coil 2 and coil 2 to coil 1 entirely.<br /><br />Then would fire on cyl 1 and not on cyl 2.<br /><br />Then replaced coil, same results. So I thought switchbox, but if switchbox, then 1 would still not work and not 2 right?<br /><br />Joe
 
A

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: '03 90hp Merc-NO SPARK!

Forget totally switching coil 1 and coil 2. Just switch the leads from the switchbox to the coils. If the spark jumps, then it is your switchbox (i.e. one of the src switches in the switchbox is damaged and isn't releasing any voltage)<br /><br />-andy
 
S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
Re: '03 90hp Merc-NO SPARK!

So off the wiring harness to the coils, I switched the harness from coil 1 to coil 2 and the harness from coil 2 to coil 1. <br /><br />I moved the spark plug leads from 1 to 2 and 2 to 1 at the same time.<br /><br />Spark moved from cylinder 1 to cylinder 2.<br /><br />If it were the switch box, would I still not have spark at cylinder 1?<br /><br />Thanks.<br /><br />Joe
 
A

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: '03 90hp Merc-NO SPARK!

2d.pdf
<br /><br /> http://www.biggerhammer.net/mercury/factory_manuals/Service Manual PDFs/TwoStroke/13645_2/2d.pdf <br /><br />This is a wiring diagram of your engine. If you switch, and only switch, the green/red and green/wht and the spark jumps from one cylinder to the next...Then it is your switchbox. <br /><br />-andy
 
S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
Re: '03 90hp Merc-NO SPARK!

The black is a ground. So, I essentially switched the green red with the green white and the no spark condition moved from top to middle plug.<br /><br />I'm leaning towards it being the switchbox too....<br /><br />I went to parts express. S/N OT793088 and they don't show a switchbox.<br /><br />My research leads me to believe that spark was decided by the trigger under the flywheel?<br /><br />Comments?<br /><br />Joe
 
A

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: '03 90hp Merc-NO SPARK!

Alright we've figured out that if you switch the green red with the green white and the no spark condition moved from the top to middle plug. Now that means either the switchbox is bad or the brown trigger lead is connecting the scr switch in the switchbox (bad trigger)<br /><br />To test the trigger Switch the brown and white trigger leads. If the no spark condition jumps from the top to middle, then it is the trigger. If the no spark condition stays on the top cylinder, then it MUST be the switchbox.<br /><br />Let's hope it is the switchbox, replacing the trigger requires a flywheel puller and a timing & sync.<br /><br />-Andy
 
S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
Re: '03 90hp Merc-NO SPARK!

I'll be at the boat later this week. <br /><br />As always, thanks for info.......<br /><br />I'll post what happens.<br /><br />Any other ideas would be great too although I think Andy nailed it.<br /><br />It is either the swtitch box or trigger(I'm thinking trigger!).<br /><br />Joe
 
A

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: '03 90hp Merc-NO SPARK!

I am guessing switchbox. They are the most common failed ignition component.<br /><br />-andy
 
cwilt

cwilt

Petty Officer 1st Class
Joined
Dec 13, 2004
Messages
208
Re: '03 90hp Merc-NO SPARK!

hey s_m <br /><br /><br />i have the same motor and year and had the same problem. i looked at every thing on the motor and could not figure it out. so i took it to the dealer they told me my ignition switch was bad , go figure!!! when they replaced it i told them to give me my old part back, later that night i ohmed out the switch ( with the help of the merc maint man ) and they were right,i never thought to look at it. <br /><br /><br />chris
 
S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
Re: '03 90hp Merc-NO SPARK!

Well, I had the dealer pick the boat up and they fixed it, I hope.<br /><br />Total charge was $137 CDN. They say they had to replace a second CDM (ignition coil).<br /><br />Now I have spark on all cylinders according to them.<br /><br />I'll post after the weekend and let you know if I'm back on the water.<br /><br />Thanks.<br /><br />Joe<br /><br />P.S. cwilt, I'm quite perplexed by your issues. Did you lack spark on 1 cylinder also? Because I thought the switch was either on or off.<br /><br />Tx.<br />J
 
cwilt

cwilt

Petty Officer 1st Class
Joined
Dec 13, 2004
Messages
208
Re: '03 90hp Merc-NO SPARK!

s_m<br /><br />sory after reading about sparks on #1,#2,#3, just got a little :confused: my motor had no spark on all three. i was getting ready to buy a stator when my buddy (eng mech who lives 75 miles away)<br />told me i should take her in. appearently the switch is not just on and off. there are six poles on it for off, run, start and choke.
 
S

steam_mill

Chief Petty Officer
Joined
Jan 16, 2002
Messages
413
Re: '03 90hp Merc-NO SPARK!

cwilt:<br /><br />I've just ordered my ignition switch changed, stator, all coils, even the motor and even my wife changed based on your comments....<br /><br />Kidding.....<br /><br />I'll report back after the Canadian and American labour day weekend on what it was.<br /><br />Tx.<br /><br />Joe
 
You must log in or register to reply here.
Top