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New project - no spark, s/n 1716455

Poco_Merc500-64

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My 1st attempt at saving a boat engine. I found lots of info over the web that helped me get to this point. 1964, Merc 500SL, 4 cyl, electric start only, no stator, no alternator, no rectifier (hence no charging system). Engine on a 1976 Trihull.

Recently ordered and still waiting for my manual. Gear control was damaged, ignition switch and wires were pushed inside housing - now fixed (I think). Was able to get starter to turn/crank over, but, no spark (on any plugs). Am about to remove Magneto and check points inside. Will look for something obvious... shorted coil?

Am I missing a step before I disassemble the Magneto assembly? Voltage reading somewhere? Impedance/resistance values?

Also, there is a red wire that is loose and hot (12/14 gauge). No idea where it goes. Don't know if this is the original harness that came with the 64 engine.

Thanks for any advice...
 
If your motor has a spark box, then there are no points to adjust (and you might break something trying to get it apart. Ah-hem!) Again, IF you have the spark box design (Lightning Energizer), the red wire goes to the red location on the spark box. It won't run without it, and it could have been damaged.

Jeff
 
Thx fastjeff. From the few online manuals available to me, I've read and seen that no spark box came for this type of old engine. A "magneto" assy, as I understand, contains the distributer cap, coil(s), condensor, and points that create all the spark needed for the plugs.

Still trying to digest how these engines work. I will not get into the carb or internal combustion yet until I'm able to figure out the no spark issue (plus the red loose wire??)

Thanks again for your input...
Alex
 
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Something to add. I've read that other 1964+ models with a charging system, the red wire was connected to a rectifier. This model I own however, does not have a charging system.

This gear control I possess with the harness/cable has that red wire, maybe is meant for those engines with a rectifier. I just dont know at this point in time.

That red loose wire seems to be paired alongside with a white wire. The white wire is currently connected to the Magneto. When ignition is turned on, the white wire reads 9.4volts (seems a bit low) and I'm not sure if this is a standard reading.

Thanks for any advice/comments...
 
Note that your motor does NOT require a battery to run--the electric starter is an accessory. (Some were manual start, right?) There is a red wire that comes off the rectifier on its way to the battery. Two, yellow wires from the stator (under the flywheel) also connect to te rectifier.

You didn't answer my question: Does your motor have a spark box that connects to the external coil and distributor?

Jeff
 
Thanks again fastjeff. I'm not sure if my reply to you on message #3 was enough info to give you an idea of the motor setup.

There is not a rectifier or a stator. I see no spark box nor an external coil. It is correct that a battery is not required to run this motor. As you stated, there is a starter (as an accessory), as well as the manual pull start.

Maybe I should just connect the red wire (12/14 gauge) straight to the positive terminal side of the starter because of no rectifier...?

Again, the magneto has a white wire connected to it going straight to the ignition switch. The red wire that runs along side it... well, that's a mystery, as well as the no spark.

I've looked at the ignition wiring diagram from maxrules.com, however i'm not sure if that applies to this 1964 motor with no charging system. Not sure if opening up the magneto is the way to go at this point... hence the questions on this thread.

Really do appreciate the expertise from this site though. You guys are top notch. Thanks....
 
Okay, so that's a good old Merc magneto motor--very reliable and easy to fix. Try this first of all:

1. Remove any wire connected to a post on the side of the magneto, then check for spark.

2. If still none, note where the flywheel and pulley position then remove the top cover and the belt.

3. Put the cover back on (belt off), bolt it up, then spin the mag CW with a drill motor. Still no spark?

4. If so, replace the belt and remove the mag (bottom part only).

You'll then have to remove the plastic parts and play with the points and etc. A good cleaning of the points with fine sandpaper, followed by a clean cloth, can bring them back. (Set at 0.010 inch.) If that still doesn't do it, you'll need to replace the condenser and, possibly, the coil. These parts are available from
oldmercs.com.

Jeff
 
Here's an update. Got no spark using the steps above - 1, 2, 3, through 4.

Magneto removed. Distributor cap opened. Checked the points... with magnifying glass even, all clean. Almost like it hadnt been getting any wear and tear. Opened Magneto. Removed coil connections, ohmed out the coil from right wire to center spring/screw = about 9k, from left side wire to center spring/screw = about 9k, from right side wire to left side wire = .4 ohms (not sure if these values are suppose to read this way).

Now, is there a specified ohm reading for the coil and condenser? I'll wait until I get more info before ordering parts... it's been a long day.

Thanks for the inputs and comments...
 
I got spark !! After removing wires and checking continuity on coil, condenser, and ground, I screwed everything back on the posts inside mag housing. Curiously turned the shaft by hand (where rotor rides on) and I got zapped !!!!!! Focus turned to mag points. Sanded it down till it was shiny. Hooked an inline spark plug checker to center of coil and ground... bam!! got light on spark checker. @#)$* WHEW!!

Now will measure and set gap between mag points (fastjeff says gap = .010), and do another point cleaning on distributor cap / rotor (I'm tempted to run carb cleaner inside mag just to clean out all the metal, but dont know if this is good). I'll assemble everything back then reset mag inside shaft/pulley/flywheel and see if I get all sparks on all 4 plugs.

Is it better to have all plugs out from block just to test spark on each plugs?? Does it really matter on these outboards?? Again this is my 1st boat engine repair so go easy on me. Are these parts inside the mag long lasting (condenser, coil, etc)?? Would it be better for me to order and replace any ignition parts just to be safe??

Thanks for any inputs/comments...
 
Magneto installed. Tested for spark on all 4 spark plugs, got all blue/white sparks. Set all the plugs wires back, primed gas into motor, turned ignition.... BAM !!! Took about 4 secs then motor started !!!! Turned her off immediately after she ran (didnt put any water under prop).

Now I'm clueless as to what I need to do next LOL. I need to read to find out if I need to change any fluid or anything else before I start her up again. @#&!! I can't believe this....

Comments welcome. Thanks fastjeff for the tips.
 
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