My Speedster had an exhaust leak as the can was installed improperly installed from the factory. It rubbed the hull and wore a hole in it.
It took alot of time to figure it out as it was difficult to see.
One clue was that the faster you went the more often it was pumping out. Next clue was the water was burning hot coming out. It will always be a bit warm because of how low and hot the engine is, but my bilge was hot hot.
I feel for you with a leak though as I bought my used and it did exactly what you are experiencing and it was frustrating to find.
My go pro was the most valuable tool as it attached a led panel light to it and put it in the bilge. I found my issue almost right away due to the fact that one I got underway, the whole engine bay went foggy. I then put it right looking at the carbon seal, and nothing. But when looking down at the seal you could see the stream coming from the right from under the exhaust can.