1966 Mercury 500 NO SPARK. ?????

joeaverage9 · Jun 16, 2013

I just bought a boat with this motor which seems to be in great condition except I dont have spark in any of the cylinders(4). The wires, cap, rotor and points/condenser all look like they have less than 10hrs on them. Spark was checked with a spark tester. I followed all of the recommendation from the Seloc manual and disconnected the harness and the negative lead from the dristributor and nothing. I adjusted the points gap to .008 as per specs. This system is fully self contained with no outside help to create spark EXCEPT the ground lead from the ignition switch to turn off the engine. WHAT I CANT UNDERSTAND IS WHY WHEN I CHECK THE SCREW WHERE THE LEAD GOES TO HAVE A GROUND ALREADY?? I removed fhe screw to make sure it wasnt being grounded out and its ok
I traced fhe ground back to the coil. Is this normal? Does anyone know the ohms values for the coil ? I have alot of knowlege with auto and motorcycle mechanics but this has me stumped. Its fathers day and damn it i want my classic boat in the beautiful florida lakes that i live so close to. Lol. Ty for your help. Joe

bgc · Jun 16, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

If I recall points should be .010 with 48 dwell. Ohms on primary 0 and secondary bout 7000.

Disconnect "shut off wire" and retry.

You show ground because the plate with the points is connected to the ground screw. Open distributor, pull the three wires from the spring end of the points and recheck.

How old is the condenser? Are the points clean? Timing belt worn out?
Its rare but the coils do fail. Some of the guys use a length of rubber hose and a drill to check the distributor outside of the motor.

emckelvy · Jun 16, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

It could be a bad coil. It's not uncommon to see them crack, then they'll arc to the case. If you remove the coil completely from the magneto housing, you can give it a good look-over. Any arc-marks and it's a Goner!

Have you tried checking spark with the kill wire just hanging there, not connected to the screw on the side of the mag? All that wire does is kill spark when shorted to ground. I've seen the tiny phenolic insulating sleeve that goes on the screw, either missing or leaking to ground when assembled to the magneto. It's just a little short reddish cylinder that slips around the screw.

Another thought, the points need to be cleaned thoroughly to bare metal and degreased, for best action. Any haze on the contacts may prevent sparks.

And I'm also recalling .010" on the points. I think the .008" spec is for the old dual-points distributor used in Inline Sixes.

To check spark with the distributor cap and rotor removed, all you have to do is spin the magneto's splined driveshaft sharply in the clockwise direction, while holding a screwdriver on the mag case with the tip of the 'driver about 3/8" to 1/2" away from the copper spring contact on the coil. It should easily jump that gap with a sharp crackle, and a purplish spark.

HTH & G'luck.......ed

joeaverage9 · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

Great idea on bench testing the distributor. I did try to test without the kill lead connected and also the engine harness disconnected. The thing is that although the points and condenser look like they have been replaced I'm not really sure. I never got to talk to the owner of the boat. My brother in law bought it and let itsit for 3yrs before deciding to sell it. The original owner is MIA. Maybe I should go ahead and replace points and condensor also. I ordered the coil from oldmercs.com but held off on the points. Is $118 the going price for points? Wow. Also I have not taken sand paper to the points contacts yet so I will do that when I get home from work. I appreciate the response fellows! Its my first boat and I am stoked about it. I will keep you posted.

bgc · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

I replace the pumps and condensers in my old gals every other year. When the condenser fails the points burn and as you see they're $120.00.
While youre in there, lube the cam. 2 drops of 60 weight oil on the wick(wick is 1/64" from the cam at peak of lobe). Tiny amount of Cam Lube on cam, too much and she'll foul the points......
http://www.jegs.com/i/Mallory/650/26015/10002/-1
http://mallory-ignition.com/distributor-cam-gear-grease.html

joeaverage9 · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

Is it OK to use 1000 grit wet/dry to clean the points? What do you use?

bgc · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

I use 400,
I cut a small strip of the paper, open the points, slide paper in, close points, and slide paper out. Keeps them closer to square...

GA_Boater · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

Hey Joe, welcome aboard.

If your magneto is like mine, the points gap/dwell is stamped inside the mag. .008/48 dwell is what's on mine.

Couple of things to check. Is the cap brush free and protrude a fair amount? Mine was stuck and barely came out of the cap. I found a new brush on ebay, I think. Make sure there is no corrosion on any of the contacts on the cap and rotor. When I have mine apart, I check for spark by holding a finger on the metal strip from the coil and turn the shaft. You should feel the tingle and no, you won't get electrocuted.

You can find parts, but expect to lose a lot of weight in your wallet. Sometimes you can find new pieces for the same price as used. Careful searching can get you the best prices. Not good prices, just a little less.

Good luck and let us know how you make out.

joeaverage9 · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

Thanks for the welcome GA and everyone else sharing your knowlege. I did get a small shock from the coil when twisting the shaft. Im gonna try to clean the points although they look clean. Never know. BTW...anyone ever heard of a Corl Tempest boat? I was told its a '68 but i cant find any info on the company. Im hooked on the classic boat scene now. I got lucky with mine. Its all original and in mint condition. Ill keep you guys posted. Thanks again.

bgc · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

Check your cap and rotor for carbon trails and cracks. Check for trails around the ground. Check for bad plug wires.
If she tickled ya, after a flick of the wrist, she has enough to light up!

joeaverage9 · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

Will do BGC. I did notice that the ends of the points where not perfectly match to each other/ not flush when making contact. I tried bending the fixed point with no success. I'm afraid to break or damage it. All I could think of using was a pair of needle nose. Would this affect it? Sounds like points are sensative and problematic like my ex wife! How do you guys straighten them?

joeaverage9 · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

We did it boys! She started on the first bump. I cleaned every contact in the distributor with 400 grit including the points which actually where dirty. I ordered a water pump kit and I'm also going to change the LU lube. Hopefully be on the lake this weekend. Thank you all very much for your help and advice. There is nothing like hearing an engine come alive after many hours of hard work! (And the smell of premix!!!)

bgc · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

joeaverage9 said:
Will do BGC. I did notice that the ends of the points where not perfectly match to each other/ not flush when making contact. I tried bending the fixed point with no success. I'm afraid to break or damage it. All I could think of using was a pair of needle nose. Would this affect it? Sounds like points are sensative and problematic like my ex wife! How do you guys straighten them?

NONONONONO!!!!! Dont bend!!!!! at's a hundred and twenty dollar part!!!!!

If the mating surfaces are creating an issue ie. burning the edge of the point due to misalignment, file surfaces square.
I pinch the sand paper between the points when cleaning them to try and keep them square.

bgc · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

joeaverage9 said:
We did it boys! She started on the first bump. I cleaned every contact in the distributor with 400 grit including the points which actually where dirty. I ordered a water pump kit and I'm also going to change the LU lube. Hopefully be on the lake this weekend. Thank you all very much for your help and advice. There is nothing like hearing an engine come alive after many hours of hard work! (And the smell of premix!!!)

Consider replacing the condenser, it'll save the points.
Good call on the pump and I would recommend doing it every other year with the condenser (keep the old ones, ya never know).
Its a great feeling when they come to life! Even better when she's screaming across the water.....
Try some SeaFoam in the old gal during the sea trials....

GA_Boater · Jun 17, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

:thumb: You can keep these old gals running and aren't that hard to work on.

joeaverage9 · Jun 21, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

I replaced the impeller but no water outof the pee hole. I cleared out he pee hole nipple that was clogged with sand and tried shooting air/ water in the hose but nothing. I also ran a thin plastic stick down the hose.I'm running it with muffs. Plenty of warm water is coming out of the grates above the prop and the piston top is very cool to the touch. I gave it a quick rev to see if raising pressure would work but nothing. If I take it to the lake how do I know if its overheating? 4th of July is closing in and I'm trying to surprise my family with our first boat ride. Thank you in advance.

bgc · Jun 21, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

Many times the line is clogged and the cavity feeding the line is clogged. Is the tell-tail coming from the top of the block out a rubber hose?

joeaverage9 · Jun 21, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

Looking at the motor from the prop side the tell tail hose goes into a nipple on the bottom left of the motor. I went to walmart and bought a tub and ran it that way. Warm Water comes out of the grilles above the prop and a small spray comes out from two square nozzles close to the bottom cowl of the motor. I grab a hose that seems to be going from cyl 2 to 3 and it was warm like water is circulating up there. The question I have is is it enough pressure?

joeaverage9 · Jun 21, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

My fiance took a video as I revved it up and a lot more water comes out of the square ports and grilles.

joeaverage9 · Jun 21, 2013

Re: 1966 Mercury 500 NO SPARK. ?????

How do I post a picture?

1966 Mercury 500 NO SPARK. ?????

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