Re: 20 and 25 Johnson difference
In my opinion nope. Leave that good running 20hp alone. That 25 parts motor will come in handy probably soon enough. Wish I had an extra parts motor for my 25 Johnson and will pick one up when the oppurtunity arises. Don't know what your running it on but I bet you'd not recognize over 2 to 3 mhp difference anyway. I live on Table Rock, it's only 50 miles or so long. So that means in my old 16' Richline and 25hp Johnson at 24 GPS MPH, I could if I wanted to go from one end of the lake to the other in about 2 hours. But it's just a fishing boat. Why would I want to.
From what I can tell from my manual the only difference would be a bigger carb and maybe the heads or piston ported/shaped differently. The 20 made it's HP at 4500rpm and the 25 made it's HP at 5500rpm. So it looks like a bigger carb/maybe porting to me. Bore and stroke/block are the same as are the lower units. Smart on OMCs part. Same pitch and diameter for the prop, just runs at a faster rpm.
Same motor, just shooting a little more gas vapor to it with maybe some factory tuning in the combustion area.
