9.9/15 hot spots

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  • March 30, 2015 at 12:35 am #1062
    johnyrude200
    Participant

      I was wondering if other people have seen a hot spot on the thermostat head for the 9.9/15’s? Attached is a picture of a good general reading I have seen on a few of these motors. I’m guessing the thermostat isn’t even opening due to cold water (about 50°), and the little bit of relief water that is circulating around the thermostat cover is hot at the top (heat rises of course).

      Is this what other people have seen? I’ve run the motor at 2/3rd throttle and that hot spot can even get up to 190-200, but the rest is staying pretty much where it should, no more than the 163° mark. The thermostat portion (bottom) was barely up to 120°. The cylinders were around 80-90°. Exhaust side (port side) was around 100°.

      March 30, 2015 at 12:01 pm #13042
      fleetwin
      Participant

        US Member - 2 Years

        Well, there will be some hot spots on most engines. The early 9.9/15s tend to run a little hotter at high speeds because there is no pressure relief system, everything must flow through the thermostat. No evidence of running hot in terms of discoloration on that head, so I would say all is OK. Thanks for taking the time to route all those leads correctly!

        April 13, 2015 at 1:00 am #13829
        johnyrude200
        Participant

          Follow up on this thread…call out to all the experienced veteran mechanics/service techs on our forums. I have a 9.5 (NINE POINT FIVE) which I changed out the thermostat, new impeller, and pulled the cylinder head and observed no clogs along with moisture around the water jacket in both the cylinders and head, yet I found with the laser thermometer that it was running between 158-166 right next to the plugs. At throttle, it was hitting near 190-200°, but the bypass temperature (up to the new thermostat) was staying within operating range. I figured at the plugs all motors run well above the recommended temperature, but wanted to cover that base as a responsible aspiring OMC mechanic/business owner.

          Maybe I’m splitting hairs (because I want to make sure when I sell something it is right), but wanted to see if this is, from an experience standpoint for all you veterans, something you have all seen? This is probably the first 9.5 that I’ve worked on in about 3 months and all the others I used a thermomelt stick on the top of the cylinder, around the thermostat housing, and to the starboard side of the top cylinder head. It’s finally boating season here in NH, and the 9.5’s are simply put, hotcakes.

          Just goes to show how using a laser thermometer yields a lot more info, and how I need to continue to accrue real-life experience (nothing in this thread really has spoken about any literature that would talk about the things I’ve asked about, or referenced and literature which ‘experencially’ speaks to this particular topic).

          There is no discoloration around the plugs or flaking paint, and it is pumping plenty of water (both with the original impeller and OEM impeller I installed today). I can post some pics if anyone needs them.

          April 13, 2015 at 9:34 am #13846
          billw
          Participant

            US Member

            I couldn’t tell you the numbers but I have always seen higher temps in close to the plugs. If you study the way a head is cast and where the water actually touches it, it’s always amazed me that the run as cool as they do.

            When our old motors were built, there were no laser guns. They had the Themomelt sticks, which were a go-no go test. The manual always showed WHERE on the block to make this test. That’s all the engineers cared about for we knuckle-dragging mechanics to test; and it should remain good enough, today, I think.

            Long live American manufacturing!

            April 13, 2015 at 11:06 am #13848
            frankr
            Participant

              US Member

              An awful lot of OMC motors are not water cooled around the spark plugs, and I would kind of guess the 9.5 probably is one of them. Unless there is a water cover over the surface of the head, you can almost assume the area is not water cooled. Of course, there is water circulation around the perimeter of the head, and heat is transferred outward to that.

              Truth is, I don’t own a laser gun, and only used thermomelt sticks when a special problem arose. Say I’m Lo-Tech in some areas.

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