Mercury - Vented Splash Cover FourStroke Series Polysoft II Marine Material 8M0228510. Overview. There is a certain comfort that comes from knowing your gear is as steady as the water is unpredictable. That is exactly how this Mercury Vented Splash Cover feels when you slip it over a hardworking 150 horsepower FourStroke. It is the kind of accessory you do not think much about until you glance back mid-run and see your engine still looking clean and sharp despite the spray rolling over the trans