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

[asterisc3]

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]

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]

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]

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]

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]

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]

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.