I have seen a few 25hp jets running around on the river here, and they were on 18-20' fiberglass river boats, both the ones I saw were 42-44" wide.
Howdy. When you say 25 jets, I suspect you are seeing factory jobs that produce 25 at the jet
, which is a lot more power than converting
a 25 prop to a jet, as was pointed out above. Another consideration is the life of the motor too, but someone more knowledgeable than me can better comment on this. That said, I was warned not to convert a used-prop to a jet because of the change in RPM. He said jets will run a motor about 5900 RPM*, higher than they're used to with a prop. For this reason, I was advised to not convert a motor from prop to jet, but instead to acquire a motor (new or used) that has been a jet all its life. *Update: The poster below is correct about the RPMs. My Mercury jet runs up to 5500 rpm with its jet, according to the spec sheet it came with.
I am about to post up my new boat in the mod section and will detail its capabilities there. But, in short, I have a 1648 Alumacraft with a 25 Merc jet... It does about 15 mph against current with 2 people and light gear. Slows to 12-13 loaded down for duck hunting. 22-23 with the current. As you note, a jet will take you great places. I run mine in 6 inches of water. Remember to keep on the gas when you hit shallow water! Gotta be on plane to run shallow!