1971 50 HP Evinrude no spark lower cylinder

Buddy told me to run motor then remove wires one at a time. I take top wire off and motor shuts off. Remove bottom one and motor keeps running.

I go to lake boat starts right up like a champ. Go in forward ready to fish and the thing won't plane and doesn't sound like rpms rev all the way. In neutral it screams if I choose to use throttle. Help would be appreciated. My ignorant opinion is that its not the carb.

Thanks Lucky Loser

Re: 1971 50 HP Evinrude no spark lower cylinder

I would verify by testing spark with an inline spark tester or and inductive timing light.

If in fact there is no spark on the bottom cylinder, swap the coil with the top one and see if spark appears, if it does, replace the coil, if not, let us know and we can trouble shoot further.

Re: 1971 50 HP Evinrude no spark lower cylinder

The lower cylinder may not be getting spark. Use a simple spark check. Remove both plugs. Use a piece of solid copper wire like that from a ground wire from house wire. Fasten one end under a bolt on the block eg one of the thermostat or case bolts. Twist loops into the wire and wrap around the plug threads. Turn the motor over with the ignition on and check for a spark at each plug. If no spark on #2 change the wiring on the coils so that #1 now is #2 and vice versa. If the spark changes places then it can be the coil or most likely the plug wire. OMC motors are prone to bad wires.

Re: 1971 50 HP Evinrude no spark lower cylinder

Well, the first test (Cylinder drop) confirms that you are only running on the top cylinder. You mention on your thread title "No Spark Lower Cylinder". Are you sure there is no spark? Have you performed a spark test? Have you checked compression on the cylinder? For the cylinder to fire you need Fuel, compression, and spark. Any one of the three could cause the bottom cylinder to not run. Figure out which one is missing, then you can begin to track down your problem.
As to running on one cylinder. A motor running on one cylinder will start and idle in neutral all day long. It will throttle up like a champ without a load. Once you put it in gear on the water, you will only get about 1/2 the RPMs you would normally get since you are only producing half the power. I had a 50 HP that pushed a piece of piston skirt through the crankcase, and I was able to limp the motor all the way back to the dock about 3 miles away running at 3K RPM the whole way.
Check the bottom cylinder for fuel, spark and compression. Once you verify which one it is, you can start to diagnose the problem.

Rgds

Re: 1971 50 HP Evinrude no spark lower cylinder

The spark test performed was by my friend who knows a little more than I do and we just used a ground from the engine. We tried the top wire from plug and you could see a blue spark. We did the same with the bottom one and didn't see anything at all.

Although, today, I pulled the lower plug out and it looked like it was wet. I also felt a small shock when I grabbed the plug wire. She still runs the same, won't plane and the rpms are down in forward speed. I pull the lower plug wire off and she still runs so I think its still not getting spark.
I'll keep you updated and try the coil switch. I'll update tomorrow after I try that test. Thanks for the advice, I'm sure I'll need more If the coil switch is inconclusive. Hopefully, thats the problem. Thanks again.

Re: 1971 50 HP Evinrude no spark lower cylinder

Ok, bought a new coil kit and replaced the #2 cyl where there was no spark. Now, it sparks great. However, when I pull the top plug cap on cyl #1 the engine will still shut down?

Should the boat keep running regardless when I pull the top plug cap? I swapped the remaining coil that seemed to work to the top with the same damn result. I'm lost now.

Boat still won't plane and seems indicative to a coil not working. Should I buy another coil kit for the top cylinder or this a waste of time ?

Re: 1971 50 HP Evinrude no spark lower cylinder

You need to do a compression check.

Re: 1971 50 HP Evinrude no spark lower cylinder

Changed plug line and coil on top and the results were awesome. Used the other coil that looked better and it worked. I will order another coil kit so I will have two new ones.

I know, I'm a lucky bastard. Could have been the changing out the plug line with the new wire from kit. At any rate, the motor is planing out running as it should. Thanks for the trouble shooting tips!

Re: 1971 50 HP Evinrude no spark lower cylinder

Glad you got it, may have been a bad connection, or plug wire, but at least now you know you have a fresh ignition system.

I think you are a little confused about your testing procedure as well. Pulling a plug wire while a motor is running, and having the RPMS drop or die, tells you that the cylinder was running as it should. Where as pulling a plug wire, and having no change in RPMS, indicates a dead cylinder.

Re: 1971 50 HP Evinrude no spark lower cylinder

You are right, Chris. Figured that out the hard way. I put the coil where it wasn't needed. Flopped em around and she ran.

Had I put it where you just mentioned I would have been fine the first time.