Johnson 1966 CD23E 6hp

I have a 1966 Johnson 6 hp which sit for 25 years. I put new points and condensor and spark plug wires in, rebuilt the Carb and the lower unit.
I used it 3 times for about a total of an hour and a half and it ran great. The next time I took it out it ran about 10 minutes at full speed and all of a sudden it slowed down to less than half speed with intermittent burst of liking it was going to kick in again. I came home and put new plugs in. Went back out the next day with no change. spark seemed a little week on one cylinder so I replace the coil again with no change. Could I be looking at a reed valve problem. Looking for ideas, thanks

Use a timing light to determine which cylinder has the failing spark.----That would be the first test I would do.----Others may take a different aproach.

racerone said:

Use a timing light to determine which cylinder has the failing spark.----That would be the first test I would do.----Others may take a different aproach.

Click to expand...

I have spark on both cylinders. I don't have a timing light but I held the spark plug against the cylinder head and got a strong spark on both cylinders

Poor test for good spark.-------Does spark jump an actual gap of 5/16" ( 8 mm ) or more, yes or no ?

Just using the spark plug and it sends a hot arc

I just tested ignition on a 1963 model 10 HP Johnson.----Spark jumps a gap of 5/16" and it runs really nice !!

I'll get a timing light.