I have a 1995 90hp evinrude and I compression tested it today. I got 85psi on three carbs and 95psi on one. From what I have seen I should have about 110+/- for each. How bad are these numbers off, and what should I do first to correct them?
the numbers do look low but they can also be due to an inaccurate gauge or slow cranking rpm as well as wear or damage inside the cylinders.
Try this first. Decarbon the enigne 2 times following the directions on the Engine Tuner can, available from your Evinrude dealer. Then give it a good run to clean things out. Then charge up the battery and recheck compression. You may see the numbers improve if the decarbonizing unstuck any carbon encrusted piston rings and if the motor is craning over faster. Use another gauge also and compare the readings.
"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.