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  • NSF-6A temperatures

    Have a NSF6A and noticed a couple things while running it today.

    1) While running under various loads up to 1/2 throttle tied to a dock, I was measuring temperatures around the engine with an IR gun. At low speeds everything was around 140 or maybe slightly less), but when I ran up to 1/2 throttle there were areas on the cylinder that were getting to 160F. Is that normal or is it an indication that I'm not cooling sufficiently? The area right around the thermostat was about 140, but the other side of the block was were I see the 160 temps. The impeller is fairly new and there is a really strong pee stream.

    2) I normally have the engine tilt pin in the most forward hole, which means the engine is tilted while just sitting at the dock. When I was idling the motor, I would notice a change in RPM going from about 45 degrees starboard to 45 degrees to port. There would be a 200 RPM drop going to starboard from where the RPM was when pointed to port. I changed the pin so the engine was level and the RPM change went away. I'm assuming this is because of the carb tilts differently when going one way vs the other and that the float bowl gas level changes ever so slightly. Anyone ever notice this? Might this indicate something amiss in the carb? (the carb was brand new ~2 years ago when I changed from a 5hp to 6hp)

  • #2
    I have power trim on my outboard. I can adjust trim from roughly -15 degrees to +45 degrees. Swivel left or right, no change in rpm whatsoever.

    Have you checked fuel pressure?

    How old is your fuel pump?
    ....

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    • #3
      Those temps sound OK. Different ventilation/cavitation or fuel level in the carb could cause that slight variation. I wouldn't worry about it.
      Paul
      Certified Tohatsu TLDI Technician
      Buffalo NY USA

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      • #4
        Well here's something interesting. Before I saw your replies I thought I'd take the thermostat out and test it. Put it in some 140 degree water and it opened up, but not very far. The spec is only 3mm, so I guess that was close.

        I left it out and went for a run. The pee stream was not as strong (expected that), but I found after I did some high speed running that the engine was up to about 140 anyways, with no thermostat. Hmmmmm. Might I have some other obstruction in there somewhere? I might pull the water pump apart too just to see if there's anything interesting in there.

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        • #5
          In the summer, the stat just helps you warm up faster, so nothing unusual there. Pee stream should be similar; the pee tube just shows you are pressurized. If in salt water. might not hurt to see if salt away helps with corrosion.

          Is there any actual problem here, or just curiosity?
          Paul
          Certified Tohatsu TLDI Technician
          Buffalo NY USA

          Comment


          • #6
            Sorry for the delay in the reply.. I wanted to check a couple things and retest. This is a long post, but I'm trying to capture all the known data.

            Yes, there is an ongoing issue and I thought/think it might be heat related.

            This issue has been going on for over a year. While you could describe it as "intermittent", it is very predictable so I hesitate to use that word. The engine will run fine for a while but then start to sputter and try to stall. I might be able to save the stall by getting out of gear and modulating the throttle, but sometimes that doesn't work.

            It is very predictable in that it will run 100% fine at startup but then depending on how much a load, it will start having problems. The most common occurrence will be starting from cold, idling out to the lake (freshwater), then getting up on plane. After almost exactly 3 miles of high speed operation (>75% throttle) the engine will start to miss and lose power, as if running out of gas. The other repeatable occurrence is if you run the engine at lower speeds for over an hour straight. When the issue has occurred, if you stop for ~15 minutes, either remove the hood or leave it on, then you can restart and everything will be fine for a while - but not as long as it took for the initial symptom to occur. If you try and restart right away, you may have a hard time restarting but the symptoms will recur shortly afterwards.

            If I run for 2 miles, stop and rest then I can run 2 miles back unimpeded. If I go 3 miles, it starts to lose power and will likely stall. If I just try and restart and head back it will periodically lose power and stall and I'll have to restart probably 10 times to get back. If I wait ~15-20 minutes after the first loss of power, then I can probably make the return unimpeded.

            The primer bulb can be pumped but it does not affect the symptoms. You can duplicate the issue on two different external tanks or using the internal tank. It is not a tank vacuum/vent issue, nor a fuel quality issue.

            If the engine stalled and you try and restart right away, it will likely not restart immediately, however sometimes the oil pressure indicator will blink repeatedly while pull starting. Normally this light might only blink at the start of the first pull, if at all. When the symptoms are occurring, you can pull 5-10 times and the light will blink. I have disconnected the oil switch to see if that was faulty and there is no difference in the symptoms. I did not actually measure oil pressure, but ruled out that or the switch when I disconnected it. The oil light does not blink or turn on when the engine is losing power, only during SOME of these restarts, if you try and restart shortly after it stalled. I also disconnected the kill switch to make sure that didn't have some kind of issue and it does not affect the symptoms.

            I've checked valve adjustment (twice) thinking that perhaps when the cylinder and valves get hot from extended operation they might be too tight, but that was not the case (I did run them with excess play once just to check).

            The last couple times I noticed the problem I had a cheap digital tach connected and it started dropping RPM quickly as the engine was losing power. To me that says it's clearly an ignition issue.

            I have replaced the CDI module twice - once with a used one and once with a brand new one (I got the new one from you, Paul)

            I have also replaced the spark plug (twice) and trigger/timing coil but not the charge coil or ignition coil. All of them pass the resistance tests in the service manual. I think I'm going to try and duplicate the resistance tests while heating the ignition coil to see if that might have an impact.


            ANYTHING ELSE I"M MISSING? It's funny that the engine is actually very reliable if you work around these patterns. I would not be concerned taking the engine across a 25 mile lake because I know it will work, it just might have a sit for a little bit in between periods of running.

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            • #7
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              Hmm. Could be a thermal electrical problem. In addition to the CD, there is the exciter coil and the pulser coil, as well as the ignition coil. Any one of those could be acting up when hot, then working OK when cool. The exciter charges the CD, and the pulser tells it when to fire.

              On the newer units, all that is integrated into an ignitor module, and there isn't any separate CD.

              The oil light will trigger when the CD fires but oil pressure is below about 4 psi, so that's normal. Plus it indicates that the CD is powering up. If I were to just guess, I would try swapping the ignition coil; it's fairly easy to swap, moderate cost, and since you do get the LED, odds are the exciter and pulser are operating OK.
              3H6060500M IGNITION COIL $43.88
              Paul
              Certified Tohatsu TLDI Technician
              Buffalo NY USA

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