no spark mystery

[robtherep]

no spark mystery <br /><br />hello i just joined and have just become obsessed with boating. i have a johnson 9.5 horse model MQ-14B no idea what year. no spark to the lower cylinder. i have installed new plugs, interchanged points,<br />condenser, and coil. always spark on upper cylinder not on lower. at one point for no apparent reason i saw spark on both plugs, reinstalled them put it all back together and took it out and it went very well with good power for 5 minutes then back to only the upper cylinder. the only component left i think is the wire to the plug, it does have continuity from plug end to the coil when tested with ohm meter. If it is the wire i can’t get at it i don’t know how to remove the plate the points, coil etc. sit on. <br />Thank you for your help.

 

[JB]

Re: no spark mystery

Hi, Rob.<br /><br />Welcome to iboats. <br /><br />MQ-14 is a 1968 engine. Good luck tracking down the problem. Could be that the lower plug wire is arcing to the block somewhere.<br /><br />Good luck.

 

[Xcusme]

Re: no spark mystery

Welcome to iboats!<br /><br />It's really no mystery at all if those are the original coils etc. Your motor looks like a 1968.<br /><br />Removal of the advance plate and servicing the ignition system of your motor is covered in a service manual, which is your next step.<br /><br />Replacing the ignition parts is an easy job. Use solid plug wires, not resistor type wire (it's available at any OMC dealer.)<br /><br />Careful attention to the manual and fresh parts should have you hitting on both cylinders.

 

[Joe Reeves]

Re: no spark mystery

The four philips screws that you see.... 2 long ones thru the coils, 2 short ones between the coils and the crankshaft. Removing those screws will allow the armature plate to be removed.<br /><br />If the armature plate wobbles bad, the following may be of some interest.<br /><br />(Magneto Armature Plate)<br />(J. Reeves)<br /> <br />If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically as the armature plate turns.<br /> <br />The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make an indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.<br /><br />You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort.

 

[robtherep]

Re: no spark mystery

thank you for all the good advice. <br /><br />68 it is.<br /><br /> didn’t think i needed a manual only to take pics as i go. but then after fixing the problem and having a gas leak then removing the throttle to cut the brittle gas line and reattach it (didn’t really have to take throttle off) 2 hours later i got the throttle back on. what’s the best way to get hold of a manual? <br /><br />I had wondered what those philips screws did. the armature plate might be loose. i didn’t quite understand enough to attempt fixing the support ring. <br /><br />sparking well now. installed new wires, coils, points and condensers. <br />one of the old coils had a black hole in it’s underside yet it worked on the top cylinder. a small engines guy i met today said that often disconcerting the kill switch solves the problem of only one cylinder firing.