Re: evinrude lower units
2K -- maybe this will help. The V4's from 1978 (as well as the 25" 1977 V4's) on have the same bolt pattern as the V6's and V8's and will all bolt up. You must use the shift rod and height adjustment for whatever motor you have. There are some differences in the spline area, but nothing you cant overcome easily. Yes, you can change a 20" and 25" shaft within the same lower unit. Just use a V6 shaft in a V6 case and a V4 shaft in a V4 case. <br /><br />As stated, there are gear ratio differences to consider. As well as propeller differences. The V6 and V8 prop shafts are larger diameter than a V4 prop shaft. <br /><br />If you need a 20" V4 gearcase, I would think it's best to get another V4 or rebuild yours. That way you can use the same prop and set up.<br /><br />It would help to know exactly what you have and what you need.<br /><br />Good luck!
