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    Over Temp Alarm Issue-gctid822029

    1998 Bayliner Ciera 2655 (Engine serial tracks to 1997 Mercruiser - Bayliner probably had extras to install in the 98's)

    5.7L 350CI 2bbl with Thunderbolt ignition

    Alpha Gen II Mercruiser Sterndrive

    Engine serial: 0K279379

    SD serial: 0L101824

    T-Plate serial: 0L101824

    Brand new impeller/housing in sterndrive (due to overheat alarm).

    Hours unknown (Had 110 on a non-original meter)

    Bought used in June 17. Since receipt, the alarm goes off once plane is attained plus about a minute (or less) at WOT. Temp gauge indicates 165ish-170 at idle through 3200rpm. Can run at 36-3700 rpm and it will go to the 175-180 mark. If I go WOT ÔÇô temp goes up rapidly and alarm sounds. Drop to idle and temp returns to 170-175ish very quickly (a matter of a few seconds).

    During a one hour run on Sunday keeping it at 3200rpm cruise, checked riser temps with IR gun. Saw about 110 on the port riser, but about 190 on the starboard riser. Today, I let it sit in the cradle with the leg in the water running at 1100rpm and the temp gauge at 170. After five-minute warmup period, took the following readings with the IR gun (all readings where applicable are port/starboard).

    Water inlet hose near thermos housing: 108

    T-Housing hose to water circulating pump: 148

    Hose to Exhaust Manifold: 112/115

    Thermostat Housing above thermostat: 114

    Thermostat Housing near sensors: 116

    Thermostat housing at hoses: 143

    Alarm/Temp sensors: 116/142

    Exhaust Manifold (taken at side near center): 104/128

    Exhaust Spacer: 108/123

    Exhaust Riser: 104/120

    Exhaust Elbow (they are aluminum): 102/141

    I could hold my hand on the port riser today, but while I could touch the starboard riser, it certainly was not comfortable, and at the higher speeds under load on Sunday it wasn't very friendly to the flesh.

    With the new impeller out of the equation, I was going to pull the thermostat housing and replace the thermostat, but now wondering if I should just suspect a blocked-up manifold. Any thoughts or similar experiences?

    Boat has been in brackish water (river watershed into harbor - gulf is about 15 miles away) most or all of its use. I have no records to indicate if/when the thermostat, housing, manifolds or risers were/have been replaced.

    TIA.
    2004 Monterey 282 Cruiser
    Twin Volvo Penta 5.0GXi-E
    SX-M 1.6gr Outdrives
    Docks @ Punta Gorda, Florida

    #2
    Sounds like your starboard riser is partly clogged. This usually occurs where the water from the engine is dumped into the exhaust and is a very common indicator that it's time to replace both risers. You will probably find that the inner water jacket walls at the mating gasket are getting thin. Check your manifolds also.

    Many here will say that five years is about when to change out raw water cooled manifolds and risers. IMO, it depends on how much and where you are using you boat. I had a friend who seldom used his boat and his were gone in five years. I had a similar boat at the time that was heavily used and I finally changed manifolds and risers after twelve years. I monitored the degradation along the way so I dint end up with surprises. You really don't want that.
    P/C Pete
    Edmonds Yacht Club (Commodore 1993)
    1988 3818 "GLAUBEN”
    Hino EH700 175 Onan MDKD Genset
    MMSI 367770440

    Comment


      #3
      Thanks for your feedback Pete. My first thought was the thermostat, but when I saw those numbers I was also leaning to the risers. Temps at the Thermostat housing and hoses seemed to be in line with what I would expect from reading some other posts. Back in my younger years I used to pull the manifolds and risers off my Renken and rod them out once in a while, but it was easier to access and I was MUCH younger!! I'm thinking I will pop the riser off and inspect it next before I pull the T-Stat or consider hose replacements. Thanks again....
      2004 Monterey 282 Cruiser
      Twin Volvo Penta 5.0GXi-E
      SX-M 1.6gr Outdrives
      Docks @ Punta Gorda, Florida

      Comment


        #4
        You used a complete raw water kit including housing ?

        Have a heat exchanger ?

        If you have good water coming into the engine ( need help to find out how to tell just ask ) if you have power steering the cooler ( exchanger ) is the first stop for raw water.

        I would first check / change out the t-stat could be frozen half closed, and the relief hole in the housing could be half closed.

        Might just be time for new elbows, got to check them and the flappers.

        Post back.
        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
          Hi Chief -

          No heat exchanger. Raw water cooling (I'll add that to my profile page).

          The sterndrive pump with housing/gaskets/entire kit was replaced at local marine center shop (not by me). I pulled the feed hose at the thermostat housing and pumped about 12 quarts of water in 10 seconds at idle, so think that is good according to a Mercruiser bulletin on the process of checking stated, which would also lead me to think that the PS cooler is clear.

          Question - if the relief valve or thermostat were half closed wouldn't the port side be warmer that expected as well? I'm hoping to pop as few bolts/nuts off as possible so I don't end up with a secondary issue (broken parts). Would a half stuck thermostat make just one side run hot??

          Thanks for your assist -

          (Were you navy or CG??)
          2004 Monterey 282 Cruiser
          Twin Volvo Penta 5.0GXi-E
          SX-M 1.6gr Outdrives
          Docks @ Punta Gorda, Florida

          Comment


            #6
            Air Force crew chief.

            T-stat first, and then elbows and flappers.
            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


              #7
              Raw water cooled.

              I'm with Pete, your exhaust temps are way to hot, they're likely plugged up with rust scale. BTW The intermediate elbow above the Y pipe will usually be hotter on the backside during low idle speeds, that's where the exhaust gasses are being directed while water flow through that elbow is low say 600-650 rpm.
              Dave
              Edmonds, WA
              "THE FIX"
              '93 2556
              Carbureted 383 Vortec-Bravo II 2.0:1 18 1/4x19 P

              The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
              Misc. projects thread
              https://www.baylinerownersclub.org/f...56-gctid789773

              Comment


                #8
                So decision was to pull the riser(s) per all the feedback, starting with the starboard unit and as I tried to drain the manifold the plastic drain plug head snapped off. Lots of rusty water and fine particles emerged. When I pulled the hose off the elbow fitting, more water and large chunks of rust fell out. Removed the riser and manifold. Also pulled the thermostat housing. The manifold is a Mercruiser, riser was a Sierra. The riser (and 3" extender block) had no scale or buildup, and lead me to believe the PO had risers - but not manifolds replaced. It could be the manifold is original, or a first replacement of OEM, but it is very clogged and full of scale and rusty stuff inside. After pulling the plugs out of the riser and taking it to a MERC shop, they feel they are in good shape and very re-usable (we set them side by side with a new unit and there was no visible loss or thinning of materials). Current plan is to only replace the headers (probably Sierras). An inspection of the Thermostat housing showed that there are no "balls" in the passages as I have read about, but the number on the casting matches the MERCRUISER Online Parts reference for the engine SN, so I suspect the "balls" may be in the bravo type engine housings? New thermostat will go in during rebuild.

                Question - with the manifolds off, is there any way (safely) to flush the block to ensure I can get all the remaining rusty crap out of the system prior to reconnecting the hoses to the new manifolds? Seems the elbow orifice is relatively small and chunks could easily plug things up again. TIA
                2004 Monterey 282 Cruiser
                Twin Volvo Penta 5.0GXi-E
                SX-M 1.6gr Outdrives
                Docks @ Punta Gorda, Florida

                Comment


                  #9
                  Just like in a car or truck, one could, could, tightly plug the exhaust ports with rags then flush the block. There's no water that enters the manifold directly from the head so "directing" the cooling hoses that attach to the manifolds away from any entry point to the pan or combustion side would amount to the same as flushing the engine in a car. My opinion anyway.
                  P/C Pete
                  Edmonds Yacht Club (Commodore 1993)
                  1988 3818 "GLAUBEN”
                  Hino EH700 175 Onan MDKD Genset
                  MMSI 367770440

                  Comment


                    #10
                    The only ports for draining the cylinder block are 1/4" TPT. They are relatively small, and were never intended to allow rust scale to pass through them. (auto engines are typically E/G cooled)

                    As for the rust scale within the exhaust system, the critical area to examine will be the "spent" seawater transfer ports.

                    These will be multiple ports that surround the main exhaust gas chamber.

                    These direct the exhaust manifold spent seawater into the Elbow's spent seawater ports. (I.E., transfer ports)

                    If your exhaust system is equipped with Spacers/Risers, these too will have the transfer ports.

                    Example of manifold, spacer/riser and elbow.


                    Here is an example of the Volvo Penta exhaust manifold and elbow seawater transfer ports.

                    Merc will be similar.


                    A Spacer/Riser will have matching seawater transfer ports that will align with the manifold and elbow transfer ports.


                    Attached files

                    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


                      #11
                      Two things to check:

                      1. The impellor is in the drive. When they get old and fragment, the pieces drop down into the space below the pump. Look at the lower drive and there will be the water pickup holes with a plastic piece on both sides. Take loose the screw holding it and remove the plastic parts and look inside for debris.

                      2. The exhaust manifold elbow has water ports to mix water with the exhaust. The ports have a tendency to corrode and block the outlet ports. If this is so, REPLACE BOTH elbows. I seriously doubt if the elbows are aluminum. ALL the ones I have seen were cast iron.

                      The other thing you can do is to put a garden hose into the hoses going to the manifold and see if one has more back pressure than the other. If so. replace, don't even think about repair.
                      Captharv 2001 2452
                      "When the draft of your boat exceeds the depth of water, you are aground"

                      Comment


                        #12
                        Completed installation of two brand new exhaust manifolds. The risers (and spacers) were checked by Merc mechanic to be ok. Appeared to have been very recently replaced by PO. Had thermostat housing off to replace that, but prior to putting the thermostat in, I reconnected all the hoses to the housing and left the two hoses going to the manifolds disconnected. I put those each in a 5 gallon pail, and then ran fresh water from the house to the fresh water flush fitting (located on the port stern). Intent was to flush the block and circulating pump of any additional rust/crud. First two bucketfuls had a bunch of rusty looking and small particles. Third and 4th were fairly clean and the 5th found was very clean looking water. Reconnected the hoses to the manifolds, and installed the new thermostat (gaskets and insert also). Lowered the boat into the water and cranked it up. Idled, and ran it up to about 900-1000rpm. Gauge only got to 145ish. IR readings at the engine confirmed that t-stat housing was about 146, water to the manifolds was about110/130 (p/s). Manifolds and risers we're warm, but never hot. Gauge never got to the 150 mark. I thought this strange as the thermostat was supposed to be a 165 per the Merc parts list. Turns out after looking at the back of the package it is a 140 stat. Took boat out yesterday for a test. Temps were running much lower than the 175 they used to show on the gauge...in the 150 range while cruising at 3000rpm. Finally opened it up (wot) and temp slowly crept up to the 175 mark. Was running about 4200rpm for about 4-5minutes and jwas ust telling the admiral that I thought the manifolds may have resolved the issue when the temp jumped from 175 to 200 and alarmed!! Immediately backed down and while boat settled into the water and revs were down to about 1000 gauge was showing temp falling, but engine stalled. Wouldn't restart (suspect vapor locked). Checked temps with the IR fun and the risers we're at 210 (OMG). As it wouldn't start so I could get some water thru it, we just dropped the hook and waited till it cooled down on its own (sea stories, Chee's, crackers and some whine from me). Admiral wasn't happy, but when the wait was over, engine cranked up like new, and return trip was fine with temps never exceeding the 145 yo 150 area. Of course I kept it at 3400rpm or less. Ended the fun with an hour cruise thru canals at idle/900rpm and temp held at 140ish the entire time.

                        So perhaps I should now be concerned with the circulating pump?? The belt seems pretty tight - less than an inch deflection at the long run. one other thing I wonder about is the prop. When we first attempted to plane and I gave it wot the boat started to climb and the rpms shot up and the boat began settling as though the prop was cavitating badly of the stern drive had kicked up from the fully down position. Pulled back on the throttle and let it settle in the water, then increased throttle but more gradually than if I were trying to pull a skiier. It went up on plane and leveled out at 3000rpm. At 3200rpm we were doing about 22 mph according to GPS. Also noticed right after first time out the the cone ring on the rear of the prop was missing (never hit anything). Not sure why the ring is there, or if maybe the prop hub is spinning a bit if that would cause an overheat at wot.

                        Running out of ideas....as always, appreciate feedback.
                        2004 Monterey 282 Cruiser
                        Twin Volvo Penta 5.0GXi-E
                        SX-M 1.6gr Outdrives
                        Docks @ Punta Gorda, Florida

                        Comment

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