According to the iboat website, this thermostat kit is compatible with my 1993 Mercury 150HP outboard...it isn't! Save yourself the aggravation of water spraying out between the thermostat housing and the valve covers and being told that the parts are not refundable unless they are defective. I'm certain that these thermostat kits do work in some engines, just not in the outboard iboat's website references. Too bad this review does not allow criticism of iboat's customer service... I'm still waiting to see if I'll receive a refund due to their error!