2001 merc poppet valve

[NoBones]

Hi George,
You did not say if you are going by the heat horn or a
temp gauge? The pop-it valves are not that bad to service
as well as the thermostats. Your local Merc dealer should
have a shop manual which spells out step by step how to do this. A minimum of tools are required for this job.
Good Luck, and good to hear from you again, See ya, Ken