Bought a boat with a 1999 mercruiser 5.7 EFI bravo 3. It has 100 hours on it. Other than winterizing and oil changes I dont think it has had any other maintenance. This is my second season. Should I replace the manifolds and risers? When I inspect them what should I look for? There is no leaking water out of the bottom of the risers and the engine starts and runs good. Engine is always at 170 - 180 degrees. When flushing the motor last the water exhausting out of the drive seemed hotter than I remember. Should I start with an impeller and see where that leads? I know that risers are to be changed every 3 years and manifolds every 5. This boat has had little use however the age may override the hours of use. Thanks for all input.