Mercury Optimax 115 Service Manual page 512

1. Water Inlet
2. Water Pump
3. Wall of Water – If water level height is insufficient, water pump may draw in air resulting in an overheated
engine
4. Water Tube
5. Cylinder Head Cover – Removed from head for illustration, normally part of head casting
6. Thermostats (2) 143 F (61.7 C) – If stuck closed, engine will overheat at idle
7. Poppet Valve – Controls water flow at high RPM. If poppet valve is stuck open at low RPM, the engine
will not reach proper operating temperature (run cold) and will run rough at idle
8. Exhaust Divider Plate – Separated for illustration
9. Strainer Screen for air compressor and fuel rail water supply – If restricted, compressor will overheat
and tell-tale will be weak
10. Port Fuel Rail – Fuel Cooler is built into Port Fuel Rail
11. Air Compressor
12. Water Outlet from Air Compressor – Connects to tell-tale outlet on bottom cowl
13. Check Valve for powerhead flush.
14. Block Water Pressure Sensor
15. Water passing through thermostats dump into the adaptor plate, then discharges down the exhaust
16. Primary Water Discharge into Driveshaft Housing
17. Water Dump Holes Exhaust Cooling (2 each) 1/8 in. (3.175 mm) – If holes are plugged, tuner pipe will
melt and bearing carrier prop shaft seals will be damaged
18. Excess water from wall of water around exhaust bucket exits around anodes
19. Water Exits with Exhaust Discharge