Thanks Don. 898 isn't stamped or labeled anywhere. The spark arrestor plastic cover only indicates MerCruiser 288.
I've always been curious why such a cool thermostat is used in this application. Is there a problem using a 160? thermostat in a emergency which I carry as a spare? I see where newer sbc versions use a 160?. There must be some theory behind this but I'm clueless as to why!