The Voyage of the Swan
Please note! This is how we do it on the Swan. These methods have worked for us, but they may not work for you. There is always risk that unexpected damage will occur that will escalate the job and the costs. Consider these risks before proceeding. Read the entire write-up before proceeding. When we work on the Swan, we always work carefully and safely. We do not proceed if we are tired or frustrated. We never hurry. Patience is the order of the day. When in doubt, or the skill level required exceeds our own, we seek the help of experts. We recommend you do the same.
  1. The impeller on this engine is between the water pump and starter and very hard to get to. It now takes me about three hours to change the impeller on our Yanmar 3JH24 after a couple of mods to my technique. My first attempt took over twice as long.
  2. First, I bought a great 10mm Craftsman ratchet box wrench at Sears that allows me to loosen and tighten the four screws holding the impeller plate to the water pump without having to lift and re-position an ordinary box wrench. The ratchet wrench is flat (no bend in the handle) which really makes the work easy.
  3. Second, I position a clamping mirror such that I can see the area between the pump and the starter (use lights and take the engine hatch cover off to improve lighting).
  4. Third, after I get the impeller cover plate off, I use an ice pick (scratch awl or brad awl would work too) to pry the old impeller out. I just stab one or two of the rubber vanes near the axis and lever the impeller out using the body of the impeller housing as the fulcrum. I am very careful NOT to scratch the inside of the housing with the ice pick.
  5. Finally, and this is the big one, I put a large zip tie on the impeller and compress the impeller with the zip tie (all vanes in the same and correct direction) such that the impeller will fit into the housing easily. Then, I liberally grease up the new impeller and the inside of the housing with silicon grease, then I slide the impeller onto its shaft and push it into the housing. As I do, the zip tie slides off the impeller (if I greased it well enough). Then I use the flat ratchet box wrench to tighten the screws. Yes, that first screw farthest in is a bitch to start. Even with these tricks it's still a bear to do. I can't believe Yanmar designed it this way.
Some Tips for Impeller Replacement (Yanmar 3JH2E engine)
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