Honda 40 cooling mystery

Discussion in 'Outboards' started by Carlazzomark, Apr 28, 2022.

  1. baeckmo
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    baeckmo Hydrodynamics

    Wise step, since we ran out of alternatives, good luck! Looking fwd to the explanation.
     
  2. Carlazzomark
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    Carlazzomark Senior Member

    The lower end is back from the mechanic, and still is not pumping.

    To be continued.
     
  3. baeckmo
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    baeckmo Hydrodynamics

    Grrr..... Ok, first a function test: lift the pump housing off while letting the impeller and lower pump cover stay in place. Check that the impeller really is locked to the shaft "torquewise".

    Then: I previously asked if you prime the pump prior to testing; ie fill the void where the suction pipe enters before mounting the pump (don't dump water into the bearing housing though), and then fill the pump from the outlet connection, slowly rotating it BACKWARDS.
     
  4. Carlazzomark
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    Carlazzomark Senior Member

    Both done again this morning and no luck. Took everything apart again, this time including the curved intake pipe and its seals. Tested the pipe for leaks and the seals for wear. All look good. I will take the lower end to a different mechanic tomorrow.
     

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  5. Barry
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    Barry Senior Member

  6. Carlazzomark
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    Carlazzomark Senior Member

    I am in Italy, and the Italian Honda Marine is far from me. And I bought my parts from a Honda dealer, and the mechanic was also a Honda dealer (not the same one). Today I took the lower end over to a general outboard mechanic, and he thinks I was sold the wrong parts, which would mean that the two Honda guys both screwed up. I left it there for him to figure out. More to come…
     
  7. BlueBell
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    BlueBell . . . . .

    Think about it for a moment...
    Everything was working fine until you changed the impeller and it sat idle for the winter.
    What does that tell you?
     
  8. Carlazzomark
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    Carlazzomark Senior Member

    I am not sure what that tells me, as I have tried three different impellers this spring.
     
  9. BlueBell
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    BlueBell . . . . .

    Did you try the impeller that was working before?
     
  10. waikikin
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    waikikin Senior Member

    Although his seems like a different issue, we have a Honda 40 fitted to a small RIB, the tell-tale stops working so we unblock the salt crystals and it works again.. not saying this is it but doesn't always indicate a problem of magnitude.
    Jeff.
     
  11. Carlazzomark
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    Carlazzomark Senior Member

    Thanks, Jeff, but this is a fresh water boat.
     
  12. Carlazzomark
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    Carlazzomark Senior Member

    Yes, and another new one — three in total. Two mechanics have said that the impeller is fine, and I am pretty sure I can tell a bad one from a good one.
     
  13. Carlazzomark
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    Carlazzomark Senior Member

    The cooling issue continues after two and three OEM parts replacement, lots of attempts by me, and two skilled mechanics on the lower end. The lower end now pumps water, but there is still no telltale.

    To review: I have tested the thermostat, and, with the lower end off, I have put a hose nozzle in the upper unit intake pipe and water flows through the engine great (engine off). Last spring I had a problem with the vacuum line that goes to the telltale, but I check that three weeks ago and it was fine. Today after I came back from the mechanic and it failed to circulate, I removed the vacuum hose tree that leads to the telltale and inspected the lines. There are no tears or perforations (now I have to figure out how to reattach the lines -- very tight fit. Suggestions?).

    Does anyone have any more ideas? Is there maybe a part missing between the impeller housing and the intake pipe?

    If the pump is now fine, and there is no blockage as evidenced by the hose nozzle test, it must be some sort of vacuum issue, no?

    If I can get the vacuum hoses reattached, I will try to run to motor with the lower unit off and the hose nozzle pushing water into the intake pipe, unless someone says this should not be done.

    Thanks
     
  14. BlueBell
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    BlueBell . . . . .

    Can't diagnose over the Internet, sorry, it's hard enough in person.
    Just keep trying different things using logical thought processes.
    You can stop trying the same thing over and over again repeatedly, it's a waste of time and energy.
    Try and avoid unfounded "must be this" statements, simply rule them out by testing.
    Is it a cooling issue or simply a tell-tail issue?

    What other work was done in the fall?
     

  15. Carlazzomark
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    Carlazzomark Senior Member

    Last fall I changed the impeller (and oils).

    Do you know about the vacuum hose system? Could this be the problem?

    Thanks
     
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