need a thermostat... which kit to buy?

[acdc96]

my 1987 Mercruiser 260hp V8 350 needs a new thermostat. the book says it requires a 143 degree thermostat, but all the ones for sale are 140 degrees. and theirs one gasket in all the kits that looks like it blocks the thermostat from water, whats with that gasket? mine did not have one. i have a pic of a kit. any ideas?

 

[Bt Doctur]

the correct gaskets are determined by the housing that you are using

 

[Bt Doctur]

the correct gaskets are determined by the housing that you are using

 

[acdc96]

I believe i have the old style thermostat housing. ill post a pic of it. just checking everything before registering it and putting it in the water and noticed the thermostat was stuck slightly open. i cleaned it and put it in a pot of water heated to 145 degrees and held it their mid water via a piece of string and it opened but did not fully shut. so i need a new one.

 

[thumpar]

Yours is earlier and may be different from mine but the 143 is for a brass thermostat and 160 is recommended for stainless thermostat.