Recently replaced the thermostats on an OMC 1978 115.
I noticed two small grooves cut in the adapter face (powerhead side).
Sure enough, a fine jet of water would squirt from the groove.
I didn't notice this before I changed the the thermostats.

Question - are these grooves supposed to be there?
Are they a form of "telltale"?
Or should I replace the gasket, use a silicone based sealant and make
sure it is sealed 100%?

Thanks,
Ben Gray

OK - found my answer.
Thermostat housing should be sealed.