Does it matter where u have your exhaust?
My first engine will not be a very big one, and I think it looks nicer when the 2 exhaust pipes "build in" the hull next to the jet drive like on the first pic...
If the exhaust pipes are lower like in the first pic, do they get filled with water?
Can u make holes yourself for the exhaust pipes, if the back end of your hull doesn't have holes?
The exhaust tips that exit below the water line have internal flappers to prevent water from rushing in. Some water will get in but shouldn't make it past the snails on the exhaust manifolds. Yes, you can make your own holes for them. Every boat came out of a mold without any holes at all.