I built a jet boat using the Kawasaki stx 15F motor/pump combo. I had to custom build the intake, its 6x12 inches at the grate, inside measurements. I have a 14/21 OEM repitched impeller, Im getting some slipping on the hole shot, I can easily hit the rev limiter on take off, top speed is 43.

Im happy with 43mph, with the swirl impeller I was getting 3-5mph faster, I had one repitched, should be here late next week. It will have 15/21 pitch. Im hoping this will have a better hole shot and maintain top speed or gain 3-5mph. Cant wait to find out.

As a winter project Im thinking about swapping the 148mm pump for a 155mm pump.

Im wondering whats the size difference between the intake tunnel on a 148mm and a 155mm, if its the same or similiar, then swapping to the 155mm punp wouldn't be hard at all, If i have to redo the intake tunnel, thats a bigger project. I was hoping I could take the 148mm off and make the hole a little bigger in the transom and put the 155m pump on.


Any idea what gains I could expect to see with 155mm pump?

Heres the boat, this wasnt my test run from today