1966 merc 20hp no spark

woodducker

Seaman
Joined
Dec 11, 2007
Messages
69
i have 1966 20hp number 1859381. im not sure if im getting spark. this motor has the pull rope attached to the cowling (hate that) and it is difficult to check spark and pull at same time. is there any test i can run? motor has good compression and i cleaned carb. the flywheel has been removed and points were replaced. is it possible for the timing to be off? also the killswitch is missing i just have new wires ran out of cover. any help will be greatly appreciated. i hope nothing major is wrong.
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: 1966 merc 20hp no spark

Tape the kill wire off seperatly then remove the plugs and install a spark plug with the ground electrode cut off in a wire with the palms of your hands spin the flywheel and check for spark.
 

woodducker

Seaman
Joined
Dec 11, 2007
Messages
69
Re: 1966 merc 20hp no spark

thanks ill give that a try and let u know what i come up with
 

woodducker

Seaman
Joined
Dec 11, 2007
Messages
69
Re: 1966 merc 20hp no spark

ok i am able to check spark now with a modified drill and i am not getting any spark at all. i dont really want to replace any parts if i dont have to. so where should i go from here. i have the fly wheel off and i cleaned all connections with coils and condensors. what else should i try? thanks
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: 1966 merc 20hp no spark

The condensers and coils will have to be checked, most good small engine or marine shops should have a tester.
 

woodducker

Seaman
Joined
Dec 11, 2007
Messages
69
Re: 1966 merc 20hp no spark

i am now getting very weak spark using a screw driver in my plug wires. but not thru plugs. i have known good plugs as well. but i might as well replace the coils and condensors if you think it may be that.
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: 1966 merc 20hp no spark

Never just replace parts it's a expencive past time test first.
 

woodducker

Seaman
Joined
Dec 11, 2007
Messages
69
Re: 1966 merc 20hp no spark

thanks. ill try to get them tested tomorrow. maybe ill have some luck.
 

woodducker

Seaman
Joined
Dec 11, 2007
Messages
69
Re: 1966 merc 20hp no spark

i talked to a few shops here and nobody would test them. they said just replace them. Is there any test i can run at home to check the condensors and coils?
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: 1966 merc 20hp no spark

It takes a Mercotronic or Stevens ignition tester or simular tester to do the system apparently those shops just pass the saving to thier customers. I would replace the points and condensers first because of cost and try that first, they can be bought at NAPA or Sierra retailers the kit with 2 points and 2 condensers is #18-5007 and points # is 18-5153 and condenser # is 18-5205 for single parts.
 

woodducker

Seaman
Joined
Dec 11, 2007
Messages
69
Re: 1966 merc 20hp no spark

thanks lad ill do the points and condensors. ill let ya know how it turns out.
 

freddyray21

Commander
Joined
Jun 10, 2006
Messages
2,460
Re: 1966 merc 20hp no spark

weak spark could be dirty points or bad condenser. I would first dress and reset the points. Most of the time that will fix it.
 
Top