As a general statement,
Jet drives require more HP than propeller driven craft,
for the same sized vessel.
You will also burn more fuel with a jet drive.
Go cart engine will probably be too small.
Why you want a jet drive ?
Unless you need to traverse very shallow water, under 1 foot of depth,
or you plan to beach the boat frequently,
a jet drive is not necessary.
If you have a lot of weeds in the water, it becomes an issue.
Personally, for tropical fishing, where I might be positioned near
a reef break ,casting, I like to keep the engine running,
if I need to pull back quickly because of sea conditions.
With a jet drive, there is no neutral, when the motor is on,
you are moving forward.