1978 Mercury 20hp no spark to bottom cylinder

[fishon1213]

I have a 1978 Mercury 200 20hp s/n 4821964. I am only getting spark to the top cylinder. I swapped the plugs and wires and got the same result. I pulled the flywheel to investigate and found the wires coming from the stator to the rectifier had cracked and missing insulation. I replaced those wires and still the same result. But then I was thinking that the function of the stator should not effect the spark. Is that correct? Unfortunately, this motor was submerged in the river. Not by me, lol. I cleaned up under the flywheel with electrical cleaner. I do have a multimeter but am not well versed in using one. So what do I look at next to determine why there is no spark to the bottom cylinder?

 

[oldman570]

Re: 1978 Mercury 20hp no spark to bottom cylinder

If the motor was submerged and not cleaned up when it was pulled from the water, You might have more troubles than just the missing cylinder. If water was in the crankcase then there is a good chance that the internals are going to need attention. A complete teardown of the motor and rebuild might be best. I would test the compression of the motor before spending any money for parts. Any wires that are falling apart, will need to be replaced. The stator dose have everything to do with the firing of the plugs. It can be costly to rebuild older motors as some of the parts are very hard to find. At times it is better off to buy another motor of the same vintage, and use the good parts off both of the motors to make one good motor. JMO
Oldman570

 

[Mi duckdown]

Re: 1978 Mercury 20hp no spark to bottom cylinder

+^ on that oldman