Old member.....new boat!

[THEFERMANATOR]

Originally Posted by pansof5

what is a poppit valve

It's part of the cooling system. When the RPM's come up above around 2000-2500, water pressure inside the engine gets high enough it pushes the poppet valve open which bypasses the thermostats to keep the engine cooler while running under a load. Many outboards run hotter at idle than they do when running to allow them to idle smoothly, but not overheat under load. Mercury used a poppet valve, and most of the others used a spring loaded t-stat that pushed open when water pressure went up.