berkey

I am troubleshooting a 5 hp pond fountain. Gfci is tripping at start up, but holds for a split second for water to start pumping. breaker holds when pump is disconnected. I have never seen the underwater connection, but from the website it looks like a straight male/female connection. tomorrow i will throw in a rental gfci breaker to rule that out. my best guess is a leak in the connection underwater. has anyone worked on one of these before? it is a single phase 240 volt 5 horse motor. 1 capacitor for the start and 2 for run.