Hello all, first post here. My question is, the exhaust on my boat has two square cast boxes ( which are mufflers I assume). Can I just remove these mufflers and replace with 4" straight pipe? It has Gil tips with a some sort of spiral core weldsd inside. Do I need to replace these tips with one's with internal flaps? The tips are about 6" above the waterline when at rest. The motor is a 454 Mag, with stock riser's. Thanks for the help. John

Hard to say without looking at it. I would think you could do what you are talking about.
As far as the tips go, it is a good idea to have internal flappers, but depending on the angle of the exhaust you can get away with not having them. I don't have them on mine.