To me it seems that the top needs to come off for the job, although I'm not using Seadoo parts myself. It is probably possible to have the wires inside the hull through the existing cabling holes, but seems like waste of time trying to fish them and do the connections through the small space there as the top of the Spark is easy to remove and allows a clean & neat installation.
I bought exactly similar 12V power outlet from a marine parts dealer like I bought the switches for pilge pump and running lights and a fuse box for these added electrics. I already put the power outlet & switches in place in the bottom of the glove compartment, but wiring is waiting for the boring autumn evenings that I can do everything at one go incl. other seasonal maintenance. It's like 2hrs job to do & parts 60€ for everything and I'll have a high-tech Spark
I bought exactly similar 12V power outlet from a marine parts dealer like I bought the switches for pilge pump and running lights and a fuse box for these added electrics. I already put the power outlet & switches in place in the bottom of the glove compartment, but wiring is waiting for the boring autumn evenings that I can do everything at one go incl. other seasonal maintenance. It's like 2hrs job to do & parts 60€ for everything and I'll have a high-tech Spark