the issue with the 18XS/189TRX, at least from what I've seen and on my boat, is there is no rigging tube. It's a rubber boot where the rigging comes out of the hull to the motor. Now, I can come off plane and not flood my rear deck, but flood the splash well and water will get in through that boot. It's not a tight seal around the steering, shift and fuel lines. Also, the little rubber cover for the charging plug doesn't always stay put. If that comes loose when the splashwell floods, again, another point for water to get in.
Not saying this is how it is for all models, but on mine there are 2 locations in the splashwell where water can easily get in.