Mercury - Thermostat Yamaha F/VF Series Cooling System Marine-Grade Brass & Stainless Components 8M6010299. Overview. When you spend enough time on the water, you learn to trust the little things-especially the parts you never see but rely on every time you turn the key. The Quicksilver 8M6010299 Thermostat is one of those quiet protectors. It keeps your Yamaha 150-200hp 4-stroke running at the temperature it was engineered for, whether you're drifting over calm flats at sunrise or hammering thr