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1996 DT150S Overheat buzzer and light problem at low speed and idle.

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  • 1996 DT150S Overheat buzzer and light problem at low speed and idle.

    i have a 1996 DT150S Serial # 15002 - 651116 That is giving me a single over heat buzzer with the temperature light staying on. I have read a lot of conflicting information on many different forums. For example, several mentions of a poppet valve under the right side of the cylinder bank. I don't see any thing under the right bank of cylinders in the back of the motor inside the cowling that is removable to change out a sticking poppet valve or anything for parts either in any of the service manuals or parts diagrams.

    The Cyl Head Bolts are starting to turn a gulden color which in my opinion tells me the bolts are getting hot causing the clear coating to turn colors. I have had this intermittent over heat buzzer going off problem at low RPM's for as long as I have owned the boat. The engine was immaculately clean when I got it so I would suspect the engine was taken care of pretty good. I purchased the boat with this engine back in 2006 and have been having this alarm issue since purchase. It does not Alarm at high RPM as far as I can recall. Only at lower RPM's like idle or just on plane at about 23-25 MPR. The engine is on a 1994 18' Charger Bass boat. Not that it matters but figured I would mention it just in case it does matter.

    I would like to get to the bottom of this. I don't have the exact service manual for this but I do have Service Manual 99500-87D08-01E Which is kind of confusing as well since it dives into several different sizes and years and nothing specific to my engine as far as I can tell.

    Any help would be great. Possibly I should start another thread???
    Last edited by N2 Fishing; 04-07-2019, 03:53 PM.

  • #2
    you don't mention servicing the most critical component - the water pump.
    when was this last serviced? !


    • #3
      Hi Art. I changed the impeller, plate and gasket back in 2010. The boat has seen very little use since then. It actually sat for the last two years. Yes I know the pump should be changed out again for good measure. Tale tell stream is good. The problem did exist before changing out the pump. I think I went as far as suspending the T stats from a wire running across a pot of water and bringing it up to temperature to see if they opened as they should. I have not replaced the T stats yet. Years ago my research let me to believe the right bank temp sensor would be the problem. So I ordered one from Brownspoint and ended up getting a temp sensor for the throttle body :/

      I don't know the exact method for checking the temp sensors left or right side.
      Last edited by N2 Fishing; 04-07-2019, 04:38 PM.


      • #4
        impellers go bad just sitting the one side gets compressed and you lose pumping
        they need to be changed at a minimum every 2 years regardless of use
        need to start with replacement first and go from there
        Im not real famine with the DT series but with the newer models, mine is a 2006 175, (well it was newer) the tell tale is not a good indicator of the water flow through the head
        you can take one of the infrared heat guns and see where the heat maybe originating
        the T stat can be checked, similar to what you did, but fully immerse and heat slowly - a candy type thermometer will tell you what temp it opens


        • #5
          An impeller that was installed back in 2010 will almost certainly have a “set” in the vanes.

          There is almost zero chance that it will be in proper working order, it needs to be changed as a matter of top priority.

          I used to work with a guy who had a boat with a 60hp Yamaha on it. He was keen but the reality of work kept getting in the way, such that he was only able to use the boat every 18 months or so - in between it just sat there, unusued, unstarted. Every time he went to use it, he had to get the water pump changed because it wouldnt pump enough to stop the motor overheating.

          And that was after only 18 months!


          • #6
            Ok pump aside, I am going to order the impeller and get that changed out. Looking forward from that and knowing that won’t fix the issue what else should I be doing. I’ll probably change gear case oil as well.


            • #7
              When you pull the lower unit for the water pump, look to see if you have a sub-water tube (#5, fig 30 & 31) going into the water pump cavity (just below water pump)? Some models have plugs, some have the tube.

              Generally if the grommets are bad (loose, worn out), there is a chance exhaust pressure, could interfere with the water pump pulling enough water. But usually higher rpms interfere more than lower rpms, but while there inspect them. If exhaust blows through that grommet, it may be getting in water pump instead of water.

              The only poppet type/ water flow valve on 2 strokes is generally located in the water pas-sages of the cylinder heads (not accessible without removing cylinder heads). A good indication this could be a problem, if the mid-section exhaust port has a large quantity of water flowing out at idle, usually it just spits slightly. Best method to clean them, is flushing with vinegar solution for couple hours in a large container (using same solution, adding make up as needed, along with cooling periods if solution gets too hot), or removal of both cylinder heads. When flushing, using a temp gun can help locate areas getting too hot, and also show those areas cooling down as flushing progresses. Run motor in solution for 20-30 min cycles, let solution cool, then repeat, making sure solution doesn't go below water pump level.

              Good luck, post back when able to let us know what you find out.


              • #8
                Thank you Solarman. I did replace a couple of things in the lower unit when I did the pump back in 2011. The Brownspoint receipt shows I purchased and used the following when I did that.

                Water Pump Repair Kit : 17400-87D11
                Water Pump Case Bushing :17564-87D00
                Gear Case Grommet : 17566-87D11
                Water Pump Grommet (L) : 17568-87D00
                Thermostat Gasket x2 : 17685-87D10

                S/M DT150-175-200-225 Service manual 99500-87D08-01E

                For a whopping Grand total of 167.70 at the time on my limited income and budget that was a lot for me :/ I'll try to pull the lower end today and hope I don't snap any bolts. Any tricks to removing the bolts with out snapping them off if they were not greased last time I did the pump? I don't recall if I knew to use grease back then or not.

                With regards to the mid section exhaust port. How many exhaust ports are there? I know of at the prop and the three holes above the prop on the lower back side of the lower unit.

                I have one of those cheap cameras you put into holes for inspections that is linked to my camera via bluetooth or wifi and I was thinking of pulling the plugs and seeing if I can see any thing inside the cylinders as far as scoring etc.
                Last edited by N2 Fishing; 04-08-2019, 12:25 PM.


                • #9
                  One more thing or question. I saw a video where a guy suggested putting the water proof grease on the impeller blades for install so it won't grab the housing and lower plate when twisting during installation. Is this a good idea? I always thought grease makes rubber parts break down a lot easier.

                  I just purchased a '94 DT150S supplimental Service manual on ebay This morning April 8, 2019. I'm hoping it will have something in it. I'll see in a few days when it arrives.
                  Last edited by N2 Fishing; 04-08-2019, 01:00 PM.


                  • #10
                    Originally posted by N2 Fishing View Post
                    One more thing or question. I saw a video where a guy suggested putting the water proof grease on the impeller blades for install so it won't grab the housing and lower plate when twisting during installation. Is this a good idea? I always thought grease makes rubber parts break down a lot easier.

                    I just purchased a '94 DT150S supplimental Service manual on ebay This morning April 8, 2019. I'm hoping it will have something in it. I'll see in a few days when it arrives.
                    I used dish soap, can’t see why a SMALL amount of grease would hurt.


                    • #11
                      I guess some dawn liquid soap would work. Thanks.


                      • #12
                        I have been brain storming for the last week trying to learn as much as possible about my specific '96 engine. DT150S is what’’s on the engine better known as DT 150 BASS. Also referred to in the service manual as DT150STC. Then a third reference lists it as DT150STCLT for the Suzuki Parts Look up. So with 3 different naming schemes for the same exact year/model you can see how I was confused when it came to finding information pertaining to my specific engine. I did not think my Service manual covered my engine but once I put all the different pieces of the puzzle together and figured out all the different engine designations were all for my engine I realized the last section in my Service manual with the "W" ('98) has all the test procedures for my engine even though my specific BASS engine was only made from 93-97 as far as I know. Oh and I found out another interesting fact. It Looks like my engine is suppose to rev up all the way until 6500 RPM as that is when it should throw a REV LIMIT code.

                        Now armed with the correct info I got my lazer pointed hand held gun style infrared thermometer out and put a new 9 volt in it for testing purposes. It also has a spot for a K style Thermal Couple that I will use in the water for testing temps as well as taping to the block for testing cylinder temps. I'm going to get all technical and try to follow a game plan here.

                        #1 pull T stats and use the suspended in pot of water and measure the water temperature to see at what temperature they start to open and what temperature they are fully open.

                        #2 Do the same as #1 for both Cylinder temp sensors while measuring the Ohms at specified temperature ranges.
                        The resistance check for the cylinder temp sensors is as follows.
                        Water Temp F 32 / 77 / 122 / 135
                        Resistance 5.3-6.6 / 1.8-2.3 / 0.73-0.96 / 0.33-0.45

                        #3 Replace Water Pump and inspect for worn water supply bushings etc.

                        #4 Check Cylinder temperatures with Thermal Couple while engine is running.

                        I just purchased on ebay what I'm hoping is new and not a defective Monitor Gauge. Suzuki no longer sells these So at $59.00 I am a bit skeptical but the seller offers a 1 year warranty for this Monitor Gauge. Worse case scenario I return it if it's defective and look for another one until I find a good one. I left my boat outside in the weather for the last 2 years and now the Rev Limit light is not working so I don't know what exact code I am getting. The only thing that happens now is the Temp Light stays on when the Buzzer sounds. The Rev Limit light use to work before I left it parked outside. Heck now the trim gauge don't even work. The RPM gauge was not working at first until I revved the engine in the higher RPM range.

                        I'm getting closer to getting to the bottom of this.

                        Edit: It looks like the Monitor will throw a temp alarm if up to 7 minutes after starting the Starboard side reaches 100C and Port side Reaches 120C. Then 7 minutes after starting it will throw a code at 83C Starboard side and 120C Port side. This comes right out of the manual. It don't sound right but it's in the manual so I'm thinking this may be why it does not sound the alarm right away after shutting it off and starting it back up right away. After restarting the engine the Starboard side has a higher range before it sets the alarm off for the first 7 minutes.
                        Last edited by N2 Fishing; 04-10-2019, 03:31 AM.


                        • #13
                          Do ya'll think it will make a difference if I skimp on the pump and get this after market one on ebay?


                          • #14
                            while you are trying to solve a problem you now want to use an untested product?


                            • #15
                              Ok I'll go with factory Suzi parts.