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1988 Johnson 88hp cooling syatem

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  • 1988 Johnson 88hp cooling syatem

    Hey everyone - I just got a (new to me) 1988 Johnson 88 Special. It runs great, and I want to make sure it stays that way!

    I want to replace anything in the cooling system that I can - thermostat, water pump kit, and anything else.

    A newby question - I can't find anything about a thermostat! Is it possible this engine does not have one? I need to be able to start this engine in below freezing temperatures (duck hunter) .

  • #2
    It came from the factory with 2 thermostats.----And thermostats have nothing to do with starting in below freezing temperatures.

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    • #3
      All engines have one, except small portable ones. A thermostat in excellent shape is mandatory for any engine to work as it should. If used without one in very cold wate temp, engine will not be able to reach its correct working temp, will probably try to fail, consume more fuel and last way less than it was built to last.

      Happy Boating


      Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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      • #4
        Since it's new to you, might be worth pulling the heads, head covers and posting detailed photos of them if you get any cylinder head above 160 degrees after replacing impeller and TSTATs or leaks at the head gasket.

        Also, there is a service bulletin/known issue if that one has the plastic carb bowls. They like to warp without warning and cause problems, you might want to replace them with the new metal ones at a suitable time but its not an urgent matter. It requires special part number intermediate jets for your model should you choose to replace it.

        Definitely recommend factory service manual, compression tester, torque wrench, and IR temp gun.

        The Seloc and clymer manuals should used be for leveling tables and drink coasters, not engine service.
        Last edited by havoc_squad; February 4th, 2019, 11:37 AM.

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        • #5
          Thermostats aren't too hard on a flatback x-flow motor. Watch for corrosion on the three mounting bolts, and make sure the little bleed holes are clear. Some say enlarge them slightly to reduce chances of blockage as blockage will cause low speed overheat. Also make sure the water intake grille on the leg isn't broken up - fragments can work through the system and get stuck in small places.
          '83 Springbok 16' with Franken Xflow, in Southern Alberta. If it ain't smokin', it must be broken.
          Avatar: "Ship Arriving Too Late to Save a Drowning Witch" - Zappa
          My 90-140 engine up-build thread: http://tinyurl.com/hz8uv47


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          • #6
            OK, waiting on my factory service manual to arrive, so I can check out the thermostats.

            I've also had recommendations to install a water pressure gauge. Anyone have any info on that?

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            • #7
              Regarding the thermostats, I will reference a good iBoats forum topic thread reference for V4 crossflow thermostat servicing:

              https://forums.iboats.com/forum/engi...moval-question

              You will probably though appreciate having the service manual to keep track of things that you have to move or remove to get to the thermostats.

              Originally posted by Big.Band View Post
              I've also had recommendations to install a water pressure gauge. Anyone have any info on that?
              Unless you are a skilled DIY'r who's done a lot of engine rebuilds and drill/tapping holes messed up, I would advise against this step unless you are doing this work on a spare part. Assuming this is something like an exhaust cover, or engine head/engine head cover you are installing the gauge in.

              If adding this sensor involves the engine block, I'd say send it to a professional that does this regularly or forget the idea.

              If you mess up on a good spare ordered to do the work, you are only out the cost of the spare part and got the original un-modified.

              If you do this only on the original and mess it up. Depending on what it is, you might be in one big hole of a problem (pun very much intended) and at the mercy of used parts supply for sale that might not be available new.

              As for me, I really don't see much of a value of an extra sensor for water pressure. You can have great water pressure and still overheat.

              I'd rather add something to have an accurate temp gauge for my 1990 Johnson 90 HP and keep the buzzer alarm than to have a pressure gauge and buzzer.

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              • #8
                The factory pressure gauge used to tap into the pisser hose with a TEE fitting.----Easy as can be to install.----Just need to cut a wee hose.

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                • #9
                  ?? But wouldn’t the issue be water pressure in the cooling passages? Unless the 88 is unique (and it might be), water at the tell-tale doesn’t indicate that water is properly circulating through the engine.

                  If a dash gauge is desired, a surface temperature gauge might do the job if one can be found. No drilling required.

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                  • #10
                    The 88 HP block is identical to the 90 /115 HP blocks.------Marketed initially without oil injection and power trim / tilt. ----Factory water pressure gauge was installed using the pisser hose.

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                    • #11
                      Originally posted by oldboat1 View Post
                      ?? But wouldn’t the issue be water pressure in the cooling passages? Unless the 88 is unique (and it might be), water at the tell-tale doesn’t indicate that water is properly circulating through the engine.

                      If a dash gauge is desired, a surface temperature gauge might do the job if one can be found. No drilling required.
                      If the primary issue that comes up is the condition of the water pump, the pressure gauge is fine. It just gives more specific data than what the tell-tail shows.

                      However, the tell-tail does not show the water flow output of the thermostats, nor does it give you any data on if the heads are overheating.

                      That is the key bit of information that is needed regarding this motor.

                      The only way to know is the buzzer alarm or mounted temp sensors on the top of the heads.

                      I suggest temp sensor on top of both heads because the TSTAT relief hole clogged up on the TSTAT housing valve body is a big cause of low speed overheat issues.

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                      • #12
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                        A water pressure gauge is your first line of defence for overheat prevention. Tee into the pisser line as R1 said, remembering that the pressure in a system is the same anywhere from pump to outlet. The pisser fitting has a fairly small hole compared to the ID of the tubing hence acts as a restriction.

                        Surface mounted temperature senders are perfectly acceptable but slower to react than if you tapped into the cooling jacket. But remember your objective is to monitor for overheat, not micro-manage your cooling.

                        Having said the above, I drilled/tapped two places on each of my cylinder head water covers and have dual pissers and wet temperature sensors. The sensors are wired to a SPDT switch so I can check head temps on the fly. I usually run the switch on the STBD head as that's the one that is more likely to overheat as it is higher. I connected my pressure gauge to the original fitting for the pisser. Tapping for pissers at the top of each head also reduces the chance of airlocking as it provides an air bleed at the highest point in the system. OMC looped the pisser line over the higher head to achieve a similar goal.
                        Last edited by interalian; February 8th, 2019, 09:34 AM.
                        '83 Springbok 16' with Franken Xflow, in Southern Alberta. If it ain't smokin', it must be broken.
                        Avatar: "Ship Arriving Too Late to Save a Drowning Witch" - Zappa
                        My 90-140 engine up-build thread: http://tinyurl.com/hz8uv47


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