Hi all, I thought I would check the impeller today. I have a load of spare impellers (came with the boat) and it was just a bit of light relief really - I had fitted the other storm window, put a bit of sealant along the hull to deck joint, fitted the replacement prop boss plug, fitted the nylon rollers on the new anchor roller and I just thought it would be wise to see how easy it is to do. Well... joy of joys it is easy to get at and the little bronze cover is attached with knurled knobs... just twisted them and off they came.. all went well and I levered out the old impeller with a couple of screwdrivers and I was quite pleased with myself. One thing did surprise me - the instructions said to undo the little screw but it just came all the way out with screw in situ. Not to worry, I put a cable tie around the new impeller and tried to slot it in - no joy! I thought I was not aligned with the slot (mine has a slot - not a hole for the screw)but no matter what I tried it would not go in! Anyway I took it out and compared it to the old one - they were not the same - the internal diameter on the old one is about 12mm and the new one is less - maybe 10mm. Whatever next - I checked the part number and the new one was correct for an MD6! I can only assume that someone has changed the water pump at some stage and all my spare impellers (4 of them) are no use to me! I just put the old one back in and I have ordered the correct size replacements. Lesson learnt - check everything!!!