Waterpump impeller is same for the Mercury 350 2-cylinder as that used on the 500 4-cylinder, on up into the late 1980s. OEM part number for the impeller is 47-89983. Sierra aftermarket number (used by iBoats) is 18-3007.
Ignition points might be a bit harder to find, as I think Sierra discontinued them. Part number was 18-5140 (OEM #398-2202). Might be able to find them by Googling around a bit if iBoats doesn't have them. The tune-up kit with condensers is 18-5008, also discontinued, but might be found on a shelf somewhere....
