If that the one made by Johnson Before they went under and I think it is then it uses the same lower unit as the 15 2 stroke. The power head is of course completly different. I think they are good engines but only made a couple of years so may be hard to fine parts for the power head.
The 15HP 4 strokes made since bombardier took over are actually Suzuki motor with Johnson name on them and the motor has no parts the same as the 2 stroke 9.9 and 15. The Old 9.9 and 15 2 stroke Johnson and Evenrude motor probably sold more motors than any other motor ever so parts easy to get.
I just checked and 2003 is when Bombardier took over so I think that is the Suzuki motor and I know nothing about it. Since it says Johnson I think you can get parts from Johnson dealers but I would check first.
