Not an expert on your motor, but compression should be at least >60 psi to run half way decent. Your rings may be stuck from years of sitting and coked up with harden carbon. Prior to the advancement of 2 cycle oil in the early 1960’s, outboard motors in general use plain non detergent SAE 30 wt motor oil mixed with gas. The motor oil did not burn as complete as the newer 2 cycle oil of 1960′ s or today. Also the motors of the era prior to thermostats ran cooler, so less complete burning of the 2 cycle mix. All these scenarios combined allowed easier build up of carbon coking of piston rings and exhaust ports and creating limited to no movement of the rings thus creating poor compression.

Poor compression prevents adequate intake of fuel air mix into the crankcase and thus limited to no combustion despite good spark.

Try squirting fuel oil mix directly into the cylinder via the spark plug hole. If ignition spark is good then there will be combustion within a couple of good pulls.

To help soften the coking of carbon around the rings and on the rings, try placing the piston midway in the cylinder above the exhaust ports and pour Seafoam, Marvels mystery oil, or Evinrude engine tune product. This will hopefully allow the products to soften the harden carbon and free up the rings. Replace the spark plug and place the motor flat with spark plug facing up for a couple of days. Pour out the mix and turn over motor a handful of times. Clean off the plugs and recheck compression. Hopefully you get improved compression if the compression is low due to stuck piston rings.

Worst case scenario would be to remove the piston and perform a manual soaking to free the rings. Of course if the ring and cylinder bore is worn out of specs then the above measures will not help improve compression.

If the motor starts some with squirting fuel oil mix into cylinder then it can sometimes loosen the carbon stuck rings.

The above measures are cheap try to increase compression if carbon coking of the rings is the cause.

Please keep us informed.

Hopefully Garry or Frank will see this and give an experts opinion on what to do.

Cajun.