1967 Mercury 20 no fire

[wbmiller3]

Replaced points and condenser $$$$$ still nothing. Kill switch is disconnected (hope that's correct for troubleshooting) coils look great but so did everything else I replaced. Previous owner said it was running great and just completely died when underway. Compression was good so I bought it. Everything on this year is super expensive, a pair of coils is over $200. I just dumped $100 into points and condensers so I hate to punt now. Anyway to check these coils with an ohmmeter? Don't want to wind up with $400 in a yard ornament...but for a good running 20 merc I'd be all smiles

 

[60sboater]

The res. between the small coil wires (primary winding) should be 1 ohm or less . For the secondary winding,ohm between the contact in the spark plug boot to ground...should be about 6-7 K ohms.

 

[wbmiller3]

That's exactly the response I was hoping for! Thanks so much

 

[RCO]

I had a 64 35hp last summer with the same ignition system that I couldn't get spark out of. It had weak magnets on the flywheel, the only one I have ever seen in working on hundreds of outboards. I had a lab scope to help find the issue. I could watch the coils build voltage, and the field collapse when the points opened, but never enough to spark compared to a known good magneto. FWIW you can swap in $17 OMC coils to the original laminations, then fit matching OMC condensers with some minor spark plug wire rerouting.

 

[wbmiller3]

Do you know which OMC coils and condensers? Looks like I have bad coils, which means both went out simultaneously...strange .8 ohms between primary's (both) and not diddly squat from inside plug boots to ground. Do these plug wires just stick into the coils or are they non-removable? Didn't want to jerk on them, don't know why, garbage I guess

Thanks Guy's

 

[wbmiller3]

BTW any advice on stator removal? I've got a factory service manual which say's "rotate stator plate in a clockwise direction and pull off" well it rotates just fine but it doesn't seem like it wants to pull off. Manual didn't say anything about removing the 2 large screws from the rotating assembly which is attached to the stator (moves stator when throttle is turned) didn't see anyway it was going to lift off with these attached so I removed them. Just don't want to force anything. If the high voltage leads have just pulled loose...not sure if I'm going to be thrilled or pissed.

 

[60sboater]

I have a '67 20hp:the stator rotates to a point where it will release and can be lifted off the base. The plug wires disconnect from the coils. If you get them free,ohm them for continuity.

 

[wbmiller3]

Got the stator off. One plug wire had pulled completely out of coil, the other seemed to be in but hard to tell. Just to recap my primarys ohmmed fine, secondarys were open. Obvious why one was but not the other. When ohmming the secondary's do the primary's need to be hooked up to the stator plate? Just use any ground on stator? Trying to check coils independent of plug wire but had to unclip and slide off the coil to get a lead into the secondary hole on the coil. Anyway to check them when unclipped from stator assembly?...confused, good info here though, Thanks

 

[60sboater]

I just ohmed my secondaries and the stator is setting on a wooden table: #1 is 6.48K and 2 is 6.68K...using the stator as a reference.

 

[wbmiller3]

Everyone except me is likely aware of this but just in case: new plug wires seem to have carbon guts instead of a steel wire. You won't get a reliable ohm reading through them. Took several hours to figure out this was my problem. Coils ohmed fine without a plug wire nothing with the wire attached. Thanks for all the help...I'm sparking now. Still can't figure the anode situation out. Looks like at some point in time my plate was removed, faired over and painted. Thinking about just sticking a bar somewhere.

 

[wbmiller3]

Now that it's all back together I'm confused about which plug wire goes to which plug, any easy rule of thumb as opposed to try starting both way's (twin cylinder)

 

[60sboater]

One should be marked "top". It's a small band.

 

[wbmiller3]

No labels, plug wires circle around under stator. was hoping someone might have one and remember that "in direction of stator rotation when opening throttle, coil closest to the plugs goes on top etc... Guess I'm just being lazy, I know I could take it all apart and see which set of points is opening with which pistons at TDC, trying to get out of pulling flywheel. In a perfect world you'd have a 50/50 chance but I've never heard this engine run so I'm kind of doubtful that it's just going to fire right up, hate to troubleshoot more than one thing at a time. Thanks for all your help. Makes me wonder how many good old engines are scrapped due to faulty connections between coil and plug wire.

 

[60sboater]

My top wire is the right-hand one as it goes through the retaining loop on the front-bottom of the stator and goes to the left-hand coil.

 

[wbmiller3]

Still no fire....new points, condenser, plug wires, coils ohm-med out ok, everything looks nice and clean, 110 lbs compression, kill button is disconnected. PO said was running great then just quit. Right after purchase I pulled the flywheel and the plug wires had pulled out of coil, thought for sure that was the problem. Evidently it's not the only one. Suggestions?????

 

[60sboater]

I'm wondering if you may have open circuits. Did you measure from plug boots to ground and get the 6-7 Kohms (shooting in the dark here)?

 

[Chinewalker]

I thought on July 12th you said you had spark? What changed?

 

[wbmiller3]

I hadn't actually tried to start it. Just assumed that since the coils checked out and both plug wires had pulled out I'd found the problem. And yes after properly installing plug wires they both checked out from plug caps to ground 6300 and 6500 ohms. Even bought a tester that clamps to ground in-case I wasn't making a good ground with the plug when visually looking at plug gap/electrode when I pulled it through. Nothing. There is a contact bar that the kill switch wires bolt to (there removed) which has two lugs that appear to have had wires attached as the screws are backed out some (I think they went to the points) anyway there are no wires attached to them, I'm guessing someone removed them prior to my purchase as nothing is hanging around loose. Don't think this would have any impact on firing though. I think it's just a bus bar to get the kill switch to ground the points when pressed.

 

[60sboater]

The Mercury pn for plug wire is 84-821945A56 sold many places,6' length. It's also called Packard 440 copper core wire. Are you using carbon core wire?

 

[wbmiller3]

Glad you brought that up, thought Id mentioned it in an earlier post but this thread has gotten kind of long And it may help someone else repeating it. One of my mant mistakes was going to the auto parts store and buying pre-made plug wires and cutting them to fit. When I checked ohms to ground from plug caps I had nothing. But coils checked out without the plug wire, carbon cored wires don't ohm worth a darn. Didn't know about 440 copper core wire (now I do) put some used mercury plug wires on it and it ohm-med ok. Got good wires (used) still no fire. Flywheel seems magnetic enough but don't have a clue how to check this.