no spark on 1965 merc500

[lordblitzalot]

this is one of 2 motors that came on a boat that i just got and the first time i took it out i had both the motors running at full speed but it was only going at about 10mph so i took the top off the motors and found that the throttle cables were not opening it all the way up so i pulled the throttle manually on both motors to get it to full speed (now about 26mph on gps).
but anyhow i just left the top off on both motors and drove down the willamette river about 2 or 3 miles and it was running great.
then i docked for about half an hour and came back and the motor would not start it would turn over and get gas but it seems like it is not getting enough spark to fire the motor.
the other one still works great.

any suggestions on what this could be and abouts how much it would cost to fix it?
kinda new to boating but i have worked on alot of cars.
any help would be great

 

[tmcalavy]

Re: no spark on 1965 merc500

It's a magneto ignition. Pull flywheel and check coils/point/condensors/wire connections.

 

[lordblitzalot]

Re: no spark on 1965 merc500

how can i tell if the condensor is bad when i pull it out?

 

[emckelvy]

Re: no spark on 1965 merc500

If the points are badly pitted, the condenser is likely shot. I betcha the points are dirty or gapped too small. Take them out, and clean to bare metal with sandpaper then polish with crocus cloth. Degrease before installing and gap to .008"-.010".

Check spark by spinning the mag shaft smartly while holding a screwdriver to case ground, with the tip approx 3/8 to 1/2 inch away from the flat copper contact coming off the top of the coil. There should be a strong spark jumping the gap. Just use caution, or you'll be the one getting zapped, not the screwdriver!!!

If still no spark, inspect the coil for cracks and burn/arc marks. It may have failed from heating up and arced to ground.

BTW the ign system is NOT under the flywheel. This motor has a belt-driven magneto.

The magneto assy is removable from the drive unit via (4) bolts. If you'll search this forum there are loads of posts regarding repair of mags.

But before you tear anything apart, disconnect the wire which is attached to an insulated terminal on the outside of the mag (note this is not the case ground wire). This is the kill wire, which grounds the mag (via the key switch) to kill spark. If there's something wrong with your ign switch, or a wire rubbing to ground, you could lose spark.

Here's some info to get you started:

http://www.maxrules.com/timingindex.html

HTH............ed

 

[lordblitzalot]

Re: no spark on 1965 merc500

found out that the motor is actually a 1966
so is this still gonna be the same as you stated emckelvy?

thanks for all the input guys i appreciate it

 

[emckelvy]

Re: no spark on 1965 merc500

'66 should still have a mag. Check the pics in the link I posted. If you don't have a switchbox mounted on the front cowling brace, and a separate, externally-mounted coil, you've got a mag.

The mag is completely self-contained/self-generating and just has 4 wires coming out of the cap to the spark plugs (and that kill wire connection on the side).

 

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[thefairlaneman]

Re: no spark on 1965 merc500

The magneto doesnt require anything under the flywheel. Its all self contained. Note the point(dwell) is very close and has to "right on the money" If you remove the rotor dont break it because it is VERY expensive to replace and dont forget the little clip that sets inside of the rotor that locks it on to the drive shaft.In case you dont know an engine with the magneto doesnt require any outside power supply to operate. the battery is just to turn the engine over not supply power to the mag.

 

[emckelvy]

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[lordblitzalot]

Re: no spark on 1965 merc500

alright got it to start.

got the distributor out and took it apart, it got some water in it somehow probably from running it with the side off, but anyhow dried that all out sanded down the points checked the gapping and now it fires up again.

however i did find out the my crankshaft is cracking on the top right around the bolts that hold the pull starter in.

but anyhow thanks for all the help i appreciate it.