Hey guys, this is the first time I have ever put an aftermarket exhaust on a boat. It's an 88 454 magnum 365hp. Now I have the diagram for the water flow but now I won't have the hose going from the thermostat to the exhaust elbow. What do I have to do? I know I have to run a jumper hose from the manifold to the back of the riser but the hose that goes to the stock elbow do I block it off somehow? Or do I have to get a new thermostat housing or what?

You'll run a Y-Jumper from the two hoses coming out of each side of the thermostat housing to a single hose going to the bottom of the exhaust manifold.

You can also take the tee out of the top of the thermostat housing and put a pipe plug in it. I've done it this way with no issue. Another option is to leave the thermostat housing as is and put a tee in the riser, this is how it is done with my gil exhaust.

I decided to make some y's out of some 316L pipe and mount them in the line so I only have the hose running to the bottom of the manifold