Reply To: New to AOMC with a 1963 mercury 200

[JayzonAych]

The majority of water discharge is directed into the main exhaust stream at base of engine block… I would not expect much air or water pressure to come out the snout or telltale without water filling the lower unit and mid section being submerged in water under normal circumstances of running the motor on a boat. Again, that muffler chamber in pan would only relief the pressure under these circumstances…. When the boats goes on plane the engine rises out of water to the anti-ventilation plate (aka cavitation plate) and the higher exhaust pressures clear the water out of exhaust housing and the pressure is nearly 100% out the prop hub. The point here is its all about back pressures.. When exhaust housing has higher water level in it, the back pressure is higher so water discharge and exhaust will pick paths of least resistance. I wouldn’t base it all with the telltale on that motor, like I said, prone to clogging. The fact that you are feeling some air pressure is a good sign…. Ultimately, the best test will be operating temperature. Depending on temperature of the water you are in, that motor will run fairly cool if all is right with your water pump since it predates the use of thermostats. Do you have a infrared thermometer? Run the motor and take periodic readings all over the engine and make sure is cooling is best advice I can give you until you build confidence… That motor will run in mid 100’s Fahrenheit if all is good… The key is to be below boiling, once boiling occurs, all hell breaks loose. These are the reasons annual water pump maintenance became recommended norm. Even modern tell tales get clogged, they are just less prone.

As far as the missing paint on block is concerned, that IS an area your particular motor can develop a leak where crankcase halves meet.. I’d say majority of mine leaked there…. My dealer friend pointed out to me there is a long span there from bolt to bolt, more than the others… He said later on later models they used the other cast in boss you will find there without holes or a bolt… However, your fuel line was also leaking so who knows… watch for it getting wet and bubbling since you replaced the fuel line…

Hope that all helps and doesn’t confuse.