It sounds like you are losing spark on one cyl. A timing light will tell you which one.
You might first try to remove the ignition coils, clean the grounds and reattach them. Also check the leads and connections at the stator, and powerpack for saltwater corrosion.
Good that you got it running. I hope it was immediately after it happened. Run extra oil in the gas for the next tank to help dry and protect the crank and bearings
The low speed issue indicates carburetion Todd.
If all's well with the ignition you are one of the lucky ones. The low tension ignition systems on that era engine were very problematic. Most dealers got OMC to pay for a CD upgrade back then.
In any event, if your certain about good spark at all times....
You may need to disassemble the carb again and, remove the low speed needle valve and thoroughly clean the carb. Double check the float level, hold the carb body uside down and let the float rest on the needle. The float should be parallel with the body of the carb and is adjusted by carefully bending the little arm stop on the float.
I suspect there is some debris or salt in the low speed circuit of the carb causing your current issue.
best of luck
Marine Mechanic
Evinrude Master Technician with 27 years of experience.