There are other guys on this forum that have a lot more primer knowledge than me, but here's some thoughts. Primer kits allow you to pump fuel directly into the carb throats. Your description of a primer bulb in the fuel supply line would be unusual. Your bulb would only push fuel into the "float bowl" (or diaphragm chamber) and on thru the pump, with the excess going back to the tank via the return line. I doubt this would help much. Gravity sends fuel into the carb this same way and doesn't need the bulb unless you think the whole system is dry and want to speed up the flow. The positive pressure in the system would not affect your bulb. My skis are older, so I'm not sure about your '97... but I think you might have an accelerator pump on one or more of your carbs. This would eliminate the need for a primer since you can just flick the throttle a few times to prime it.