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Compression ?

Discussion in 'Boats and Motors' started by FishON32, May 25, 2007.

  1. I have a 1971 40 hp mercury I'm selling and I want to check the compression. Does anyone know what it should be or where to find this info out. Thanks Nick.
     
  2. Your readings may fall anywhere between 100 and 150 psi. There is no set number for what they should read. You are mostly concerned with the variation between the cylinders. They should be within 10 percent of each other.
     

  3. Thanks Ken I had it tested and it came out 100/105.