If your oil consumption was 30:1 as figured in a previous post, you would have no mosquitos around as they would all be dead from the clouds of blue oily smoke coming out of your engines.
Most of the the time, measuring errors in both fuel and oil are to blame for excessive perceived oil usage.
Start with a topped off tank of oil and a full tank of fuel and go run the boat, keeping tabs on any fuel added to the tank until the oil level becomes very low. Fill the boat tank and add the gallons pumped since the test began. Measure the oil added carefully, some go one quart at a time until the oil tank if full again. Then do the math.
Because the oil delivery system is computer controlled and extra oil is added during starting and heavy acceleration and at rpm at or above redline, and throttle heavy boat operator will consume more than smooth throttle application.
"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.