Want to know more about how your engine is breaking-in or wearing? Curious about whether or not your oil is doing its job? Want to be ahead of problems that may develop? PartsVu has partnered with Blackstone Laboratories and we are now offering professional oil analysis kits. Results are typically received in a few days via email. Shop now.Mercury 300 Hour Service Kit 15/20 HP 8M0120838. The Mercury 300 Hour Service Kit - 8M0120838 provides the essential components required to perform the recommended 300-hour maintenance service on Mercury 15 HP and 20 HP four-stroke outboards with serial numbers 0R235949 through 0R833819. This kit combines the critical oils, filters, cooling system components, ignition parts, and seals needed to keep your engine running reliably.. Regularly performing scheduled maintenance helps protect your outboard's internal components, maintain proper cooling performance, and ensure dependable operation on the water. This kit simplifies the service process by pack