I have an 1982 Evinrude 90 HP v4 that has a chunk missing from the lower unit casing where the prop shaft comes out (about 1'' by 3/4). There is also a crack forming on the opposite side that is about 1' long. This hasn't effected the integrity of the seal/gear box yet. I am looking at lower units that are for sale. I was told by a shop that my o/b has a 20'' shaft. I'm not sure what lower units are interchangeable and would fit my o/b. Is it possible to use a lower unit with a 25 shaft and then swap my old shaft into the other lower unit?<br /><br />Thanks for any help that can be given.<br /><br />Bo