Mixing coolant types in your diesel boat engine isn’t a great idea. Even though coolants come in different colors (like green, orange, etc.), the color doesn’t really tell you if they’re compatible. Each type has its own mix of chemicals, and mixing them can mess with the engine’s cooling system, reducing protection against rust and wear. It could also make things more complicated if you need to do repairs down the line, and might even void your warranty. To keep things simple and make sure your engine stays in good shape, just stick to the recommended coolant type and avoid mixing different kinds.