'78, 50hp merc no spark on 2nd cyl.

asterisc3

Recruit
Joined
Mar 15, 2004
Messages
2
I would really appreciate some help on this. So far, I've tested for spark on all the cylinders and gotten strong spark on 1,3 and 4 so I tested the wire and the coil for continuity and they worked, so now I need help on the rest of the ignition cause I dont know anything about it.<br />Thanks in advance.
 

KCLOST

Commander
Joined
Jun 22, 2002
Messages
2,095
Re: '78, 50hp merc no spark on 2nd cyl.

Most likely a switchbox problem (my most hated subject). Check the leads that go from the #2 coil to the switchbox (probably green in color) make sure it is not shorted somewhere. <br /><br />I believe you only have one switchbox. I'm pretty sure you can switch the #2 lead at the switchbox with one of the others (they are proably all green) and see if the no spark moves from it to another cylinder....<br />But I'm not 100% sure on that, hopefully someone can answer that one, or come up with an easy test.. I wouldn't run the engine when testing, just crank it over.
 

Ken G

Petty Officer 2nd Class
Joined
Feb 28, 2003
Messages
158
Re: '78, 50hp merc no spark on 2nd cyl.

You have one switchbox and 4 ignition coils. The manual says that VOA meter tests can only detect certain faults in the ignition coils. If VOA tests are satisfactory you need to use a Quicksilver ignition Analyzer to fully check the coil. If you remove the suspected faulty coil you may find a Mercury dealer who can test it for you. <br /><br />The four coils are identical so you can switch coil positions to see if the no spark condition follows the suspected #2 coil. If the no spark follows the #2 coil that is your problem, if the no spark stays with the #2 cylinder your problem is probably in the switchbox. Make sure you disconnect the battery before working on the ignition system.
 

Greg New Zealand

Petty Officer 3rd Class
Joined
Dec 7, 2003
Messages
98
Re: '78, 50hp merc no spark on 2nd cyl.

My '77 Merc 50 has one coil and a distributor. If yours is the same it wont be a coil problem. Check that the #2 plug lead from the distributor to plug. Swap the lead over with one of the others to check whether it's just the lead. Try the same with the plug.
 

KCLOST

Commander
Joined
Jun 22, 2002
Messages
2,095
Re: '78, 50hp merc no spark on 2nd cyl.

I'd like to see his serial# before I'm sure.<br /><br />But Greg, I don't thing he has a distributor. He should have 1 switchbox and 4 ignition coils. All four coils are covered up with one cover. The switchbox releases the spark to the coils via a signal from the triggers.
 

Greg New Zealand

Petty Officer 3rd Class
Joined
Dec 7, 2003
Messages
98
Re: '78, 50hp merc no spark on 2nd cyl.

KCLOST. You may be correct. Just remembered that my 50 has a recond '74 powerhead so may be a different beast. We need that serial #.
 

asterisc3

Recruit
Joined
Mar 15, 2004
Messages
2
Re: '78, 50hp merc no spark on 2nd cyl.

thanks for the advice everyone i will get to testing that coil as soon as i can get to it. it was covered in snow so i havent had the opportunity to get to it.
 
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