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 key maintenance components needed to properly service Mercury 15 HP and 20 HP four-stroke outboards with serial numbers 0R235949 through 0R833819. Designed to simplify scheduled maintenance, this kit includes the oils, filters, cooling system components, ignition parts, and seals required for the 300-hour service interval.. Performing routine maintenance at recommended service intervals helps protect internal engine components, maintain proper cooling system function, and ensure reliable performance on the water. This kit packages everything nee