Mercruiser 8.1L Coolant Reservoir Testing

[Helmling]

Purchased a STANT Engine Coolant System Pressure Tester PN 12270
Does anyone know the part number for the adapter to connect to Mercruiser 8.1L Coolant Reservoir?

 

[makomark]

best thing to do is to measure the thread size on the reservoir and then look up the adapter.

12026 is very likely to be it....but I've never tried in on an 8.1....