Tohatsu 4 Stroke MFS 2/2.5/3.5A Outboards Service Manual, Page 56Get this manual
23) Inspection of Cooling Water Passages 1Check water strainer for cloggingClean if necessary
Set outboard motor in the water and start engineCheck that cooling water is discharged from cooling water check port 2If not, check water pump and cooling water passage in the engine2