Re: Exhause flaps
If they are thru the hull, you cant miss them. Usually 2 2"-3" holes cut out thru the back of the boat. Never had a thru hull exaust so I cant tell you how to look or check them, but I have had several I/O and here is how to check to make sure that they are still there.
If your boat is an inboard/outboard then they are usually located in your exaust Y pipe that sits between your motor and transom. You can easily look for these by loosening the 2 circle clamps on either side of the exaust system that comes off the exaust manifold and elbow. you only have to loosen 2 of the 4 circle clamps as long as they are on the same side of the rubber hose that connects the exaust elbow to the Y-pipe, preferrably the side that on the Y-pipe and not the manifold.
Remove the 4 bolts that hold the exaust manifold to the Cyl head and then start wiggling and twisting the manifold/elbow around to remove if from the Y pipe. Be carefull to not hit the spark plugs or if you are able to then remove them prior. If you look down 2" give or take a little you should see the flappers in the exaust.
Do not forget to get a good exaust manifold gasket set to replace the one between the Cyl head and the exaust manifold. Once you pull off the manifold you should replace the seal.
This is for most Mercruisers. All others are up for grabs.
