Re: checking impeller ??
The impeller is inside the water pump housing, which is sitting directly attop the lower unit. So you can't see it without removing the water pump housing, which means removing the lower unit. By the time you go through all the work to see it, you might as well throw a new one in. They're cheap, they don't last long (only a few years notwithstanding use, replace it every 1 or 2) and if they let go, you loose your engine. And if you frequently dissassemble your water pump, you don't have to worry about it all corroding together. See the 65ish Lark 7 post for details of that.<br /><br />You want to have a manual in hand, but taking off the lower unit on your engine is no problem. Just remove the window on the side of the leg and disconnect the shift linkage. You have to completely remove one of the two bolts for it to disconnect. Then remove the 6 small and 1 large bolt holding the lower unit on. The l/u should now pull off.<br />When you reinstall it, make sure the o-ring at the top of the driveshaft is in good shape, and lightly grease the splines with marine grease. No shift adjustment is necessary as the shift rod connector bolt keys into the shift rod. If you pull on the driveshaft while the water pump is off, it'll come out of the lower unit. No big deal, just gently put it back in. Coat all the screws and bolts in sealer (not RTV silicone!) before re-installing them. This will make removal next time much easier. If the water can't get to it, it won't corrode.
