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  • 1996 88 SPL OVERHEAT

    Over heat alarm going off at cruising speed but stops at lower rpm. From research I'm thinking possibly thermostats but more likely flow deflectors in heads. A couple questions: Can thermostat housing be removed without removing power head? To clean out water jackets in heads and replace deflectors do I access through exhaust cover or do heads need to be removed?

  • #2
    It's a hassle but you change the thermostats without removing stuff.

    ​You need to remove the heads to change the deflectors.


    • #3
      If the water pump has been serviced/maintained (fresh impeller), check the actual head temps right after a run.


      • #4
        Water pump replaced two years ago while lower unit was off for shift rod o ring replacement. Not a lot of hours on water pump since replacement. Just removed both hoses connecting heads to thermostats and ran engine on hose muffs and both sides have equal flow. If I hold my finger on one side the flow increases on the other. Now that good flow verified from both heads should I put hoses back on and run engine and check with temp gun or just move on to thermostats?


        • #5
          Put thermostat hoses back on and ran engine on hose muffs. Used temp gun and two left heads ran 145 to 150 The top right got to 160 and right bottom to 185 when I shut it off.


          • #6
            If a salt water motor or a river runner, best approach is to at least check/test the stats and replace if in doubt. Then pull the heads and scrape out the water passages. Check deflectors and replace if appropriate.

            If a lake runner, might the the t.stat work and see if temps return to normal -- 140/150 is OK, but on muffs probably lower (typically about 40 degree temps from the hose).


            • #7
              Thanks oldboat1 it's a saltwater motor (southeast Louisiana). Pulled the thermostats and both are dirty and corroded right side worse than left. I'm hesitant to attempt to pull heads because of age and saltwater use. Concerned with possibly breaking head bolts.


              • #8
                Checking in late -- maybe made a decision already. Busted bolts are a possibility. Could first do the t.stats and see what you get.

                If into the bolts, soak what you can (might only get into the bolts heads, but that's something anyway). Try rapping the bolt once or twice, then using a box wrench and tapping sideways each direction on the end of the wrench.


                • #9
                  Installed new thermostat kit and ran engine on hose and head temps run 135 to 140. The temp in front of heads on side of engine block where pistons are is 150 to 155. Should this temp be higher than heads? Haven't had a chance to run engine in bayous yet due to high water.


                  • #10
                    Think I would try it when it's safe to do. Sounds like the temps are normal -- fronts of heads will be hotter. Check it a couple of times to see what you have.


                    • #11
                      Kind of a big sucker, but you might rig a plastic barrel for routine fresh water flushing -- something you can slip under the l.u. when the boat is on the trailer. Use a PVC inline valve or similar and mount it at the bottom of the barrel -- lets you drain it for moving out from under the motor. Water level has to be up over the water pump (use the trailer jack to raise and lower a few inches). Run the motor at idle or fast idle to keep the water in the barrel -- good idea to keep the hose running.


                      • #12
                        Thanks oldboat1 and yea its kind of big for a drum. I'll wait a couple days for water to go down to do further testing as overheat alarm occurred at cruising speeds and quieted at slow speeds so I want to check it out under those conditions before my next fishing trip.


                        • #13
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                          I got a barrel for $15 locally. Cut the top off just below the rim and trimmed to fit around the transom bracket.

                          Rather than fit a valve at the bottom, I just siphon out the water. Easily done: you need a hose to fill it anyway, just put it down to the bottom of the barrel and run the water for a few seconds. Disconnect the hose from the tap and put it lower than the bottom of the barrel. The siphon will start by itself.
                          '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