From memory – the impeller is in the leg directly behind the propeller. I think on mine you remove the prop and then there are two nuts holding a plate where the propeller shaft exits. The impeller is behind that plate I think. I think there are slits in the housing behind the prop that are the water intake point??
I’ll try to remember to take some photos tonight.
BTW – I’ve never had to replace the impeller. I think mine still has the 25yr old original. But – My engine does not get used much (1-2 hrs a year). It does however get blocked cooling channels and every few years I need to clean them out. When I spoke to the Suzuki rep he said – run it in fresh every time you use it BUT it will probably still block up – He said the only cure is to use it regularly – then they tend not to dry out and block up. Mine blocks with a mixture of dry salt, mud and oil.