Marine: Boating, Sailing, PWC, GPS and Navigation - Is my motor pumping water properly?

I am the new owner of an old boat ('74 Chrysler 90HP). My first trip to the lake (today) was cut short because I wasn't sure the motor was pumping water properly. At idle and speeds just above idle you can see a nice jet of water spewing out, however, by the time you reach 1/4 throttle or so there is no evidence of any water being ejected. Is this normal or do I have a bad water pump.

I have never worked on a chrysler so I'm not sure how the cooling system is set up. If it were mine I would put a impeller in it just to be sure, they should be changed every 2-3 years.

Welcome to the board.

I tried to find verification for this, but couldn't. My aging memory tells me that the telltale hole is simply tapped off the main outlet, and the main outlet continues down the lower drive and out below the water line.

When the motor is idling the pressure is too great to allow all of the water to escape under the water line, so it bleeds out the telltale hole. As the boat goes faster, the pressure is relieved. Less water goes out of the telltale hole and more leaves through the main outlet.

Again, check me in case I'm wrong, but I believe that motor has an overheat buzzer.