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Changing the impeller in the raw water pump is a regular maintenance item for our engines and it was time for us to do this.
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Since we have owned our boat for about 7 years I have replaced the impeller before and done it on a friends Universal diesel as well. After an overheating incident about 6 years ago I replaced the entire water pump with a new one on the sound advice of Don. You would think that with this kind of familiarity with this engine component that changing the impeller would be a 'snap' for me.
One of the main obstacles we faced is the access to this component on our Tartan 27. First we tried removing the 4 screws on the back plate which revealed the impeller. We were able to pry the old impeller about an inch out of the housing but it was impossible to remove the clip and impeller with the access we had. The shaft of the water pump could be persuaded to come out of the pump housing about 1" but would come no more.
Either my memory is failing me or I have worked on different model Oberdorfer pumps where the shaft would smoothly come all the way out of the pump housing and be easily re-inserted. On our pump the shaft is NOT removable unless pulled from the inside as the shaft diameter is larger on the inboard side then the impeller side. We figured this out after we gave up fussing and cussing at it and just removed the 2 bolts that hold the pump to the engine so we could then work on it in a shop. I am glad we did not try to pull the shaft out the wrong way by brute force as we surely would have ruined the seals for the shaft and had larger problems.
Sometimes tasks that we think should be difficult are easy to do but this experience was more the inverse. Had we removed the pump from the engine in the first place it would have qualified as an easy task. Sometimes memories have a way of being misleading as well. I will make a note in my MMI A4 manual about this so I do not repeat the relatively short lived frustration this simple task caused.
<background>
Since we have owned our boat for about 7 years I have replaced the impeller before and done it on a friends Universal diesel as well. After an overheating incident about 6 years ago I replaced the entire water pump with a new one on the sound advice of Don. You would think that with this kind of familiarity with this engine component that changing the impeller would be a 'snap' for me.
One of the main obstacles we faced is the access to this component on our Tartan 27. First we tried removing the 4 screws on the back plate which revealed the impeller. We were able to pry the old impeller about an inch out of the housing but it was impossible to remove the clip and impeller with the access we had. The shaft of the water pump could be persuaded to come out of the pump housing about 1" but would come no more.
Either my memory is failing me or I have worked on different model Oberdorfer pumps where the shaft would smoothly come all the way out of the pump housing and be easily re-inserted. On our pump the shaft is NOT removable unless pulled from the inside as the shaft diameter is larger on the inboard side then the impeller side. We figured this out after we gave up fussing and cussing at it and just removed the 2 bolts that hold the pump to the engine so we could then work on it in a shop. I am glad we did not try to pull the shaft out the wrong way by brute force as we surely would have ruined the seals for the shaft and had larger problems.
Sometimes tasks that we think should be difficult are easy to do but this experience was more the inverse. Had we removed the pump from the engine in the first place it would have qualified as an easy task. Sometimes memories have a way of being misleading as well. I will make a note in my MMI A4 manual about this so I do not repeat the relatively short lived frustration this simple task caused.
