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    temp alarm threshold-gctid396356

    2001 5.0 carbed m/c. Seems like my temp alarm comes on way too soon lately. Like around 5* above op temp.Normal op temp is needle on middle of the "5" on 175 on temp gauge. Alarm goes off if it gets to rh side of 5. Occurrs sometimes on slowing to idle after a long run,etc. Could be a pump issue but it seems to me alarm shouldnt be coming on till 200 or so?I am fw cooled and have a 190 therm installed. This never used to happen so something has changed. Either Im not pumping as much rw as before or alarm sensor has gone off its spec. im thinking. I am about due to change rw impellor but there are no indications of gradual or slight overheating while running as I would have expected if imp on way out.Any thoughts anyone?

    Specs for alarm sensor?

    #2
    There will probably be lots of different opinions on this one, but I would question your choice of 190 degree thermostat. I say this only because I believe that coolant temperatures are harder to maintain a relative constant in many marine applications opposed to a road vehicle. The reason being is the relative difference of the heat exchanger temperatures. Another factor could be the ambient temperature in your engine space. It is true that higher engine temperatures make for more efficient combustion, but really, 180 degrees should be adequate. Why not try a 180 degree 'stat and see if that solves your problem?

    As for the actual temperatures you are reaching and what your alarm setting is, often gauges are not very accurate. An infra red temperature scanner can give you a pretty good idea of what your temperatures are and at what point the alarm trips. I'd be inclined to check this first to see if your concerns are valid. I would be comfortable with a high temperature trip point of about 200 degrees F.

    As for the temporary increase in temperatures after a slow from relatively high cruise, I experience this as well and don't believe it to be abnormal.

    Comment


      #3
      My Bayliner original temp guage used to stay at 180 degrees whatever (once warmed up of course). My new Faria guauge and new sender swing around like a demented child. I mention this because some gauges seem to smooth the ride and others just don't.

      As mentioned earlier it is only an IR gun that will give you an accurate reading (and you have to use the gun carefully as well - hold it 2" away from the area you want to measure). A IR gun will tell you if the engine (or more accurately) the temperature alarm sender body is reaching the threshold (which should be 210 degrees with a little tolerance). You can point the gun's red dot on the alarm sender (not the temperature guage sender) and see what it is reaching.

      Good luck. I hate overheating problems. It is a good thing these engines are built to last.

      Terry
      Terry (Retired Diving Instructor and Part Time IT Consultant)
      1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
      MMSI 235061726

      Comment


        #4
        To run with a t-stat or not run with a t-stat has been a question debated many times and on many boards.

        I don't run a t-stat and none of my friends do in a marine engine that is.

        My questions before i offer a opinion:

        1- When was your t-stat last changed or tested ? 190 is way to high 140 would be my choice if i were to run one.

        2- Risers checked last ?

        3- Flappers / shutters checked last ?

        4- Heat exchangers checked last / cleaned last ?

        5- Drive is ? Bravo, alpha, what ? Reason for this question ? Bravos are different could be cause, water pickup issues.

        3 years tops on impellers yours not changed within 3 years could be the problem right there.
        Be good, be happy, for tomorrow is promised to no man !

        1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

        '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

        Manalapan N.J

        Comment


          #5
          I'm with Robert on this. Lower the temp rating of the thermostat a bit....., and give it a try.

          Keep in mind that a thermostat, in a RWC'd engine, holds back coolant within the engine only, and releases it on an "as required" basis.

          All other sea water is by-passing the actual engine cooling demands, and is directed into and out the exhaust system.

          This all takes place within the RWC'd T stat housing porting.

          If your alarm temp sensor reads engine temp, then a cooler stat should render an immediate improvement.

          If the alarm temp sensor reads exhaust temp, then a cooler stat make not make a noticeable difference.... which likely leads you to a sea water pump issue, and/or exhaust manifold/riser restriction issues.

          As for a debate regarding Stat or No Stat, we'll see a minority only who believes that NO STAT is acceptable.

          Marine Engine Manufacturers equip these engines with a temperature controlling thermostat for good reason.

          We also do not want to haphazardly choose a temp rating for a RWC'd engine.

          Let your water influence the decision.

          Lake or River water....... keep the temp up where it needs to be.... perhaps 160-ish* or so.

          Ocean water..... keep the temp lower (where it needs to be) in order to control Salt Crystallization. The magic number seems to be 140-ish*.

          .
          Rick E. Gresham, Oregon
          2850 Bounty Sedan Flybridge model
          Twin 280 HP 5.7's w/ Closed Cooling
          Volvo Penta DuoProp Drives
          Kohler 4 CZ Gen Set

          Comment


            #6
            Thanks for the responses. I am FWC.I believe this makes 190 an ok thermostat?Or not?

            Interestingly,when I converted to FWC and installed the therm that came with kit fr. San Juan, the thermostat I replaced, which SEEMEd to be the original(no paint off bolts etc)was a 190 also. I didnt get boat brand new so some history missing.Very little if anything had ever been done to engine so that therm. may remain a mystery I guess.

            My drive is Alpha g2.

            I may just do the impellor anyhow I have a spare. I keep boat in water and use it all year round, have found that impellors last for years that way and usually give warning signs like a slight increase in op temp long before failure.I know this runs against accepted wisdom but the continual soaking as opposed to long periods of trailering does make a diff IMO. I developed this theory before I found this forum.

            Still puzzled by the alarm thing, reasonably sure but not positive it used to allow more degrees before sounding off.

            Comment


              #7
              Using the boat more frequently certainly helps with impeller life......, but 'ole Father Time takes it's toll on impellers regardless.

              Those three/four vanes that remain folded, just can't retain resiliency forever.
              Rick E. Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Comment


                #8
                Thanks for the responses. I am FWC.I believe this makes 190 an ok thermostat?Or not?

                Interestingly,when I converted to FWC and installed the therm that came with kit fr. San Juan, the thermostat I replaced, which SEEMEd to be the original(no paint off bolts etc)was a 190 also. I didnt get boat brand new so some history missing.Very little if anything had ever been done to engine so that therm. may remain a mystery I guess.

                My drive is Alpha g2.

                I may just do the impellor anyhow I have a spare. I keep boat in water and use it all year round, have found that impellors last for years that way and usually give warning signs like a slight increase in op temp long before failure.I know this runs against accepted wisdom but the continual soaking as opposed to long periods of trailering does make a diff IMO. I developed this theory before I found this forum.

                Still puzzled by the alarm thing, reasonably sure but not positive it used to allow more degrees before sounding off.

                Comment


                  #9
                  Apologies for reposting same post. Must have hit a wrong key.

                  Comment


                    #10
                    Our 2003 2359 also runs a bit higher temp since we changed the combo tach/temp/oil pressure guage due to tach failure. (tap-tap no more though!) Ours is also 5.7L with A1 G2 and this is our 3rd season without changing pump. Bear in mind we stay out of the gravel and sand and never rev on flush kit or run dry- ouch.....

                    Our temp is somewhere around 180 F , above the 175 mark. No changes to engine, just 1 winter older. Old guage read approx 170 F

                    IMO the temp guage is just an indicator at best, relying on clean connections from sender to guage thru harness plug since it works on resistance ground from the sender.

                    The temperature alarm switch is a normally open switch that closes on temp limit to provide a ground to the control system. Those normally close at around 200 degrees if fully functional. If memory serves the tolerance is +/_ about 5%. These are often Cole Herse 1/8 pipe thread and relatively cheap. These are cheap devices and not milspec reliable and should be #1 suspect in my experience. You can easily x ref to cole catalogue and get them for under $20 not $50 plus.

                    Merc Man #24 calls for 160 F for all engines, including closed cooling. I think both the Merc and SJ closed cooling can be block only or block and manifolds.

                    If you have fresh water cooling on your exhaust manifolds the closed cooling system has a bigger job to do and needs to be in top shape. If your Raw Water exits to the risers and not the exhaust manifolds you have the full system vs the half system. You would have aslo installed blocker plates in between your risers and exhaust manifolds for the full system.

                    [COLOR]"#000000" wrote:
                    You can test both your Tstat and temp alarm switch [/COLOR]with a pot of boiling water and a 220 deg thermometer - you could also contact SanJuan and see what tstat they recommend for their cooling system on your engine. Ours was installed as supplied and is the full FWC SJ system.

                    We`re on the Island now, waiting for some good weather if it ever stops raining. Enjoy your heater up there!!

                    Adding the following link which is a good read on FWC types and applications. It also specifies a 160 F tstat.

                    http://www.perfprotech.com/store/art....aspx#fwc-full

                    telstar1 wrote:
                    Thanks for the responses. I am FWC.I believe this makes 190 an ok thermostat?Or not?

                    Interestingly,when I converted to FWC and installed the therm that came with kit fr. San Juan, the thermostat I replaced, which SEEMEd to be the original(no paint off bolts etc)was a 190 also. I didnt get boat brand new so some history missing.Very little if anything had ever been done to engine so that therm. may remain a mystery I guess.

                    My drive is Alpha g2.

                    I may just do the impellor anyhow I have a spare. I keep boat in water and use it all year round, have found that impellors last for years that way and usually give warning signs like a slight increase in op temp long before failure.I know this runs against accepted wisdom but the continual soaking as opposed to long periods of trailering does make a diff IMO. I developed this theory before I found this forum.

                    Still puzzled by the alarm thing, reasonably sure but not positive it used to allow more degrees before sounding off.
                    2003 Trophy Pro 2359; Rebuilt 5.7L Vortec longblock (crate) using rest of the previous owners freeze destroyed 5.0L. Now fully FWC Alpha 1 Gen 2 drive.

                    Comment


                      #11
                      Jeez I must be loosing it. 160 was what I should have wrote. My therm is 160 as was the old,rwc, one.

                      Thx.

                      Comment

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