1969 Johnson 25R69D

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  • June 8, 2015 at 6:34 pm #17811
    Mumbles
    Participant

      An outboard Tstat should open around 143 F. to keep the temperature within safe limits. Above 160 F or so, salts and minerals in the water can leach out and build up deposits in the water jackets. This is why only TCW III (Two Cycle, Water Cooled) marine oil should be used in an outboard motor as it is designed to burn off at the lower operating temperatures.

      When you check your motors temperature, you’ll find hot spots and cold spots but generally the top of the block and on the starboard side where the welch plug is are good places to check.

      June 8, 2015 at 10:46 pm #17822
      morelor
      Participant

        Great info Mumbles! I’m going to try to get some temperature readings this weekend. If does turnout that the temperature is higher than 160 even after an impeller change what could be the cause? Will it still pump water good even if there is a blockage somewhere in the cooling system?

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