need evinrude impeller for a 4hp

[mgcodcatcher]

hi,still trying to find the right impeller but were all coming up with nothing,here is the model number e4brcta-serial b015389,tag number 390692 and 8-b1-bl.im dead in the water with out the right impeller its alot smaller the my over 4hp and it has a steel nut in the middle and has a pin and not a square key.hope you all can help.more poeple who can help me the better,many thanks matt.p.s i think its a 1983 evinrude....