Re: 1973 JOHNSON MOTOR
Next time you have the time, run your motor on a "hose muff." Be sure to place the muff over the horizontal, grooved openings on either side of the gearcase, between the under side of the cavitation plate and the hump where the gears and prop shaft reside. After starting your motor, you will observe water coming out of a couple of pee holes that are below the where the waterline would be if the boat were in the water. Now look for the vertical groove/openings above the cavitation plate just above where the prop mounts. When you first start your engine, you will not see water exiting here but it should right after the thermostat opens up. If you don't see water coming out here within a minute or so, you have a problem.
I agree with the advice to replace the water pump impeller if you have no idea when this was done last.
The 1973 model motor does not have a factory installed telltale exiting at the bacl of the lower cowl, as do the newer motors. As others have said, it is easy to install one. I have seen them mounted into the exhaust cover on the port side and in various positions on the head. Whatever location you choose, be sure to seek adequate advice and instruction before drilling holes in your motor.
PS: I agree with gbell - I don't think you will see water exiting from the two exhaust relief holes located on the upper, rear portion of the midsection.
