I agree it will work - just not well. Do not know about the rivers near you but here in SE PA a 25 jet will not be enough to get around - the Delaware river in particular has a very very strong flow.
Now you need a jet head for that motor!
Keep in mind that you will still need enough HP to get your boat up on plane for teh jet drive to work in shallow water. "We lose about 30% of the HP when converting from propeller to jet drive. With less than 25 HP, it is difficult to plane a boat with two people. If it won't plane, it will not operate successfully in shallow water."
https://www.outboardjets.com/faqs.php#Why dont we make jet drives for less than 25 HP