Mercury - Quicksilver 8M0177107 Thermostat Gasket 9.9-60hp Outboard Series Composite Seal 8M0177107. Overview. If you've spent enough early mornings easing away from the dock, you know how much trust goes into every small part of your engine. Something as simple as a thermostat gasket plays a quiet but essential role in keeping things running smooth and steady. When the water's cold, the sun's not up yet, and you're headed to your favorite spot, you want to know your outboard will warm up the wa