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Yamaha 250 4 stroke overheating alarm

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  • Yamaha 250 4 stroke overheating alarm

    I have twin 250 Yamaha 4 strokes on my boat and recently the overheating alarm has been going off on the portside engine while trolling or at idle speed. I can turn the engine off an back on and the alarm will stop for a minute or so but then will reactivate once again. I changed the waterpumps and thermostats out on both engines in hopes that my problem would be corrected however that has not been the case and now the alarms on both the port and starboard engine is going off at low idle speeds. I know the alarm is controlled by a sensor on the front of the motor but was not sure if the sensor is actually my problem or if the problem could be coming from a blockage somewhere that is restricting the water being passed through the engine. I am new to the forum and would greatly appreciate any advice.

  • #2
    Re: Yamaha 250 4 stroke overheating alarm

    The first thing that is needed with any post is the model identity. It can be found on the left hand clamp bracket data plate.

    How many hours on the motor?

    In addition to a sensor, the over temp alarm will be activated if either one of two thermoswitches close.

    A pressure control valve that is failed open will cause insufficient water to flow through the block at low RPM's and cause an over temperature situation. So too can a failed mid-section due to corrosion. That is why it is important to know the model of the motor, how old it is and how much time is on the motor. Saltwater or freshwater usage?

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    • #3
      Re: Yamaha 250 4 stroke overheating alarm

      Are you positive it is overheat alarms that are coming in?

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      • #4
        Re: Yamaha 250 4 stroke overheating alarm

        I'm away from the boat for another 4-5 days but it's a 2007 yamaha F250's used in saltwater. Each motor has 1750 hours. I service it regularly and always flush each engine after use. I was wondering if it was the PCV valve or possibly a seal on the lower unit?

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        • #5
          Re: Yamaha 250 4 stroke overheating alarm

          Originally posted by 99yam40 View Post
          Are you positive it is overheat alarms that are coming in?
          Yes sir I am positive that it's the overheat alarms.

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          • #6
            Re: Yamaha 250 4 stroke overheating alarm

            Have you determined if its actually overheating, via temp gun?
            What condition where the thermostats in?
            What rpms are the motors at when the alarms go off?
            When your alarms go off at higher rpms does your engine go into protection mode?
            Everybody wants to go to the party. Nobody wants to stay and clean up.

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            • #7
              Re: Yamaha 250 4 stroke overheating alarm

              Originally posted by hall832 View Post
              Have you determined if its actually overheating, via temp gun?
              What condition where the thermostats in?
              What rpms are the motors at when the alarms go off?
              When your alarms go off at higher rpms does your engine go into protection mode?
              The alarm only goes off in in idle speed between 6-800 rpms. The alarm never goes when the rpms exceed 900. At higher speeds all works great its just at the lower rpms that I have the alarm activation. Three of the four thermostats were corroded pretty bad when i changed them out and one was still in fair shape but I changed it also.

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              • #8
                Re: Yamaha 250 4 stroke overheating alarm

                PRV if stuck open will not let block fill up due to dumping too much water at low RPM, which will cause top cylinders to not have cooling water in the passages

                But Overheat alarm should not clear that quickly by turning off and then right back on again.
                Takes a while to cool the metal in the motor

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                • #9
                  Re: Yamaha 250 4 stroke overheating alarm

                  When you did the impellers did you do the water pump housings as well?
                  What condition are the housings in? (most people just change the impellers and not the whole pump)
                  i agree with 99yam40 on the poppet valve. trying to see what has been done to date
                  Last edited by hall832; October 8th, 2013, 05:23 PM.
                  Everybody wants to go to the party. Nobody wants to stay and clean up.

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                  • #10
                    Re: Yamaha 250 4 stroke overheating alarm

                    Originally posted by hall832 View Post
                    When you did the impellers did you do the water pump housings as well?
                    What condition are the housings in? (most people just change the impellers and not the whole pump)
                    i agree with 99yam40 on the poppet valve. trying to see what has been done to date
                    Hi Hall832 and the rest of our iboats members that are trying so graciously to help out cflowe with his overheat question. I'm Just dropping in to let you know that since cflowe if new to the forum life, he has accidentally hit the report icon while replying to a question to Hall832. You will find his reply quoted below this message. I would have sent him a private message, but sometimes the newbies don't seem to find them right away.

                    PS, While i am here, On behalf of iboats, I'd like to thank everyone for all that you contribute to the forums each day. Without you sharing your knowledge, these boating forums would be a dull place to spend time on. So thank you all.

                    Please carry on guys, and good luck cflowe.

                    The Mod squad.

                    Originally posted by cflowe View Post
                    Yes I changed the impeller as well as the housing and actually the old ones did
                    not look that bad. I may have been misleading as far as turning the engine off
                    and then right back on actually I leave it off maybe a minute or so before
                    turning it back on.
                    OEM Quality Gear Lubes And Greases Available @ iboats.com 'By Bel-Ray Marine Lubricants -- BOAT SPECS -- FORUM GUIDELINES -- Volvo, OMC & Merc Stern Drive Technical Information For DIYers. -- OEM VOLVO PARTS POWERED BY iBOATS.COM -- All OEM Parts / Parts Lookup Now Available Through iboats.com --

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                    • #11
                      cflowe, I'm having the some issue with my 2006 250 Yamaha 4 stroke. Overheating alarm at idle speed and everything ok at higher rpms. That went on for sometime. Now the motor will idle for a little bit then dies but still performs great at higher rpms, but when it comes down temp alarm comes on. I did everything you did (water pump, thermostat, PRV, checked fuel, plugs, etc... finally had it hooked up to the yamaha computer and it indicated that all is great with the motor (really?). But i still have the same issues. Did you find out what the issue was with your motor?

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                      • #12
                        Originally posted by jcwaters1 View Post
                        cflowe, I'm having the some issue with my 2006 250 Yamaha 4 stroke. Overheating alarm at idle speed and everything ok at higher rpms. That went on for sometime. Now the motor will idle for a little bit then dies but still performs great at higher rpms, but when it comes down temp alarm comes on. I did everything you did (water pump, thermostat, PRV, checked fuel, plugs, etc... finally had it hooked up to the yamaha computer and it indicated that all is great with the motor (really?). But i still have the same issues. Did you find out what the issue was with your motor?
                        If you want answers, please start a topic all your own. This is way past the 90 day limit and the original poster is long gone, so don't expect an reply from him. Look at the Rules in my sig below.
                        BOAT SPECS | FORUM HELP | STARCRAFT FORUM | SHOP iBoats
                        Please, no PM's (Private Messages) regarding boat/engine problems.
                        That is what the forums are for.
                        Only forum/moderator issues will be answered in PM's.

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                        • #13
                          I have the same problem with my f250 2006 any update

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                          • #14
                            Sign up today
                            I have the same problem with my f250 2006 any update overheat at idel speed only

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