I am replacing my port side heat...

[coltsneckbob]

I am replacing my port side heat exchanger and want to also change thermostat.  I have a 2002 340 Sundancer with 8.1S.   

Looking for advice on what is the temp rating I need for the thermostat.  And good online site that sells them.  Thanks

[Andymlow]

Usually the old thermostat will have markings that tell you the temperature rating

[340_Sundancer]

take a look at page 47 in your mercruiser owners manual. It's a 160 degree thermostat