I am changing the Thermostats in my 2000 500 EFIs. I am not sure where they were when I winterized them. I think they should go in the intake manifolds under the thermostat housings.
I found a couple of Mercury parts diagrams but they are confusing. On my Thermostat housings the cup or brass sleeve is solid in the housing so i thing the thermostat and cork ring should
go under the housing not on top of the housing under the top cover with the two hoses for the CMI Headers. Can some one confirm this ?
Thanks in advance, Rich

The thermostats are under the plenum on top of the intake. Regarding the thermostat stack up you will need serial number. There are a couple different stack ups dependent of serial number / year. Really need that info.

There is different place depends on engine numbers , some went in the intake and some in right below the top cover . You really need serial number to know where the " correct " place . Mine is a 2001 and mine is under the top cover

Mine Is 0L601027

Hopefully link works:

http://www.mercruiserparts.com/bam/s...31337/4889/150

I have seen that. That is the one that is confusing to me. The only thing I can figure out is #8 #9 #10 goes in the thermostat housing from the bottom. My problem is on my motors #10
is fixed solid in the housing so the thermostat goes under the housing and sets in the intake. At least that is the way I see it ???