Putting a 25" lower on a bass boat is kinda like pushing a chain....it just don't work. Even with a jackplate. The problems that it will cause are many. Swap the mid to a 20" inch and you would be good to go. Even with the jackplate you would at best get to about 4 1/2" or 5" below pad. The performance would be extremely poor
Here is one way ta tell what it is. On tha down housing at tha "lower" motor mounts. They have a plastic cover being held with two screws. Measure from tha bottom of tha plastic cover to tha cavitation plate. Don't remember tha exact measurements but a 20" they will be real close together. A 25" will be 4 maybe 5" between the mounts and cav. plate. 30" even more. Look close at tha lower mount on this one. Click on it to enlarge. You can see how close tha lower mount bolts are to tha cav. plate......20"