I am going to say the stop switch is going bad #1. Even if he pulls the lanyard, it won't stop, because of the way the circuit is in the switches. The only way to kill it is to disconnect the battery.
Have him start by swapping the switch assembly with a good one- this is easy enough to do without much effort. That can determine if the switch is really at fault.
As for it building RPM's, I have had a few skis do this- and yes, low fuel can cause it for some reason. An exhaust leak (a small one) can cause this as well, not enough to have it free rev, which I have seen happen as well. You really need to see it firsthand yourself, and not take how he is describing it to you. "Building RPM's" is kind of a poor description.... he may just need to adjust the idle, or he could have a poorly adjusted throttle cable that is slipping if he is revving it as he flushes, etc. etc.
I am going to say the switch is going bad, and the other problem is attributed to user error or some minor mechanical problem. But you have got to go hear/see it for yourself.
Have him start by swapping the switch assembly with a good one- this is easy enough to do without much effort. That can determine if the switch is really at fault.
As for it building RPM's, I have had a few skis do this- and yes, low fuel can cause it for some reason. An exhaust leak (a small one) can cause this as well, not enough to have it free rev, which I have seen happen as well. You really need to see it firsthand yourself, and not take how he is describing it to you. "Building RPM's" is kind of a poor description.... he may just need to adjust the idle, or he could have a poorly adjusted throttle cable that is slipping if he is revving it as he flushes, etc. etc.
I am going to say the switch is going bad, and the other problem is attributed to user error or some minor mechanical problem. But you have got to go hear/see it for yourself.