Is your Mercury outboard's oil warning light acting up? This is the genuine Mercury oil tank switch and sender unit, part numbers 87-856156T02 or A2. It replaces the older 87-856156A2. This part monitors the oil level in your engine's oil injection tank and sends the signal to your dash warning system. Fits a wide range of Mercury outboard motors from 135 horsepower all the way up to 300HP. Brand new in the box (NIB). If your engine isn't getting the right oil mix signal, it could lead to serious damage. Swapping this sender can fix false alarms or, more importantly, a missing 'low oil' warning. A crucial maintenance part for any Mercury owner. Make sure your oil injection system is communicating correctly to protect your expensive motor!