1999 Mariner 45/90 Jet increased performance

Hello all! I currently have what I believe to be a 1999 Mariner 45/90 3cyl. jet (received from my grandpa on an 18ft jon boat) . The boat hull is in pretty rough shape so I was kicking the idea around of putting it onto another hull (more of a cruiser than fishing). I have seen some videos of 2 strokes being modified to produce more power and higher top speeds. Due to the age and what I want to do, I was planning to overhaul/modify the motor. Any good threads on something similar? Also any pointers or guidance would be appreciated! I'm currently working on getting the serial numbers off the engine (it is located about 2 hours away from me currently). It will run about 28 mph wide open with the jet, any ideas on how much speed will be gained with a prop swap? Thank you in advance!

Best solution would be to put a normal gear case on it.

On a serious note. Look at setup. Cant tell you haw many jet drives come through here buried all the way down.

That's a 3-cylinder it would be a 60/45 that is a 60 horsepower powerhead converts to 45 horsepower at the jet. You could gain up to 10 miles an hour with a switch to a prop but the jet motor is a 15in so you'll need to lower the motor to put on a lower unit and there will be issues with the shift shaft since the jet does not use one.