I have been driving mine with some leakage. I was able to reduce the leakage by pulling the rubber bellows and clamping it up tighter against the carbon seal.
Any leakage of water into a ski is "problematic"..... you risk the "leak" becoming a sudden failure (as it is already leaking), so is it worth the risk of a failure while out on the water? The ski could sink.....before you get it back to dry land.....personally, if I know it's leaking....it's getting fixed BEFORE the next ride. That's me though....IMHO!
If you do not have a bilge pump "any" leak is pretty serious as far as possible sinking goes. More than that a leaking carbon seal will cavitate the impeller real fast and that will also need to be replaced.