Water in exhaust pipe flood. The pipe to the back of the boat was at the top with the pipe into the water block from the engine at the bottom. Now if you intentionally shoot pressurized water into the exhaust pipe you could flood the muffler and cause enough of a blockage to cause very rough idling and hot water to spray from the exhaust. In the event that motorists are caught up in flooded waters they are encouraged to keep stepping on the accelerator. There is probably mud and sediment in there. The water block has 2 pipes at it the exhaust into it and the exhaust out of it through a hose and out of the back of the boat. But if you notice that your tailpipe is leaking or dripping water out from it then it means your exhaust system must have water inside it. If this is the reason of the water coming out of your exhaust pipe it is perfectly normal and is nothing to worry about.
If your exhaust pipe is submerged the exhaust gases flowing out will stop water running along it towards the engine. If you go too fast your bow wave will come back at you eventually flooding the engine. The water block has 2 pipes at it the exhaust into it and the exhaust out of it through a hose and out of the back of the boat. Water formed through this process should not cause alarm.
Once the flood goes down you should check your car for flood damage to see whether it was submerged in water and whether water entered the engine. This is why putting water in the exhaust pipe is wrong. Accordingly what happens if water gets in your exhaust.
Use a waterproof exhaust pipe cover. The chain needs to be removed cleaned with something like kerosene and relubed. A beer rests on this so its important. In case of car flooding the exhaust pipe is probably full of water.