Some 47s have all six exhaust out under the swim platform. On our boat (with 525SCs) the center engine exhausts out thrue holes in the curved part of the hull/platform. At idle they are under water and with silent choice on the other two it softens the noise. What I don't like about the set up is it does shake the boat while at the dock.

We have a '99 47'Lightning with 525's, extension boxes and blueprinted bottom by Fountain that does right at 90. Always freshwater boat on Eagle trailer with gen that is mint and also for sale in MD. Email me at [email protected] for info and pics if interested.