Have a tech run a full engine report and look for any abnormalities, especially in the voltage areas. Inspect the blue capacitor, take compression checks, evaluate sparkplug condition, as well as starter, cables, and battery. The motor has to crank over quickly to assist starting. Fuel pressure readings and leakdown are important.
If everything checks out, often replacing the spring in the pressure relief valve keeps the fuel cooler and can alleviate hard starting warm.
"There is never just one thing wrong with a boat";
-- Travis McGee, main character in a book series by John D. McDonald
The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.
The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.