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Over Heating : Not Clogged Jackets

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  • Over Heating : Not Clogged Jackets

    I greatly appreciate everyones advice on removing the water jackets and cleaning them out to resolve an overheating problem on my '97 Yamaha 115. Well, I just pulled the jackets off and pealed the gaskets off. It appears to me that they are not coroded at all. There are a few small rust spots but certainly not enough to restrict water flow.

    The thermosats (I'm assuming they are thermostasts) up near the top of the jacket look a bit worse for wear. There looks like there's some crud built up in the springs of one of the thermostats. Could this be the overheating issue?

    I'm not sure where to look next and would greatly appreciate any advice. I suppose that I could hook up a hose to see if water is even getting to the water jackets.

    I sure hate taking her to the local boat repair pirates, just to drop $1000.00 and not get any results.

    Thanks, Jfro Haleyhead


  • #2
    Re: Over Heating : Not Clogged Jackets

    Hey Jfro,
    If you recently lost a water pump impeller and replaced it, did it have all it's blades still attached? I have had to pull powerheads before to remove stuck pieces of impeller blade that got wedged in the entrance to the lower side of the power head. New thermostats are allways a good idea, not knowing what type of waters it is being run in, but if you want to check them....you can put them in a pan of water on the stove top and rasie the temp up and use a good thermoter to watch the water temp and check and see when the thermostats start to open. Most thermostats have the temp numbers printed on the bottom of the brass or copper looking pellet in the center of them. Good Luck!

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    • #3
      Re: Over Heating : Not Clogged Jackets

      When was the last time you replaced the water pump, thermostats, and PRV? They are all preventative maintenance items
      Thermostats are easy to test just put in a pot of water and heat it up while monitoring the water temp to see when it starts opening ,when it is open fully, and when it closes back off.

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      • #4
        Re: Over Heating : Not Clogged Jackets

        99yam40, Sir,

        Well my next question was going to be how do I get the thermostats out? I suppose that would answer your question of when did I last replace them. The water pump was flowing strong so I haven't messed with it. And, I'm not sure what the PVR is. I'd be happy to replace all of these with some guidance.

        Thank you for your help, Jfro

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        • #5
          Re: Over Heating : Not Clogged Jackets

          I just tapped the thermostats out. Wow, one of them is very clogged up with crud. It's also off of the side of the motor that was overheating. I'll bet this was the main issue. Let me see if I can attach a photo.

          Click image for larger version

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          • #6
            Re: Over Heating : Not Clogged Jackets

            looks really bad.
            PRV is a pressure relief valve that opens to relieve some of the water pressure during high RPM.
            Best to pick up a Yamaha service manual and read up to see if you want to do the servicing your self or take to someone that has the tools and knowledge. It will save you money in the long run.

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            • #7
              Re: Over Heating : Not Clogged Jackets

              Thanks again. I'll look at the manual for the pressure release valve. Cleaned up the old thermos and they both opened up at about 110*. I'll still get some new ones, but I was hoping the coroded one was bad.

              Believe me, I would rather not be doing this myself. I wished I knew of someone who had the knowledge here in Jacksonville. I'm certainly willing to pay for quality work....just can't seem to find any here in this town. I've paid at least $10,000 for boat repairs in the past and have never.....never gotten a cents worth of improvement in my vessels.

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              • #8
                Re: Over Heating : Not Clogged Jackets

                well you know what they sat if you want it do right do it yourself. well as an ex-auto tech(Igot old) even if that t-stat opens its still restricting water flow. good luck keep us posted we can help
                sigpic[FONT="System"][/. ase master tech

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                • #9
                  Re: Over Heating : Not Clogged Jackets

                  Just from what I can see from in your pic showing a very small portion of the inside of the WJ cover, it looks like it has extreme buildup.... way worse than mine had (also a 97) and I reallly thought mine was severe. "Clogged" is a bit of a misnomer..... while you might not find any passages clogged / blocked, but the scale buildup insulates the water from the water passages reducing it's ability to carry away the heat. Think of it this way... if you run a water hose on your bare skin you would feel the coolness of the water immediately, now wrap you arm with several mils of plastic and you would not feel the coolness of the water near as well, same thing is happening in your motor. Pull the heads, WJ covers & PC valve and clean all the scale out.... replace PC valve, spring and the Tstats. I would also do the water pump. I did all this to mine when I had a high speed overheat and problem solved... the first time. Here is some before / after pics of mine:

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