Re: 1977 evinrude 9.9 water pump problem
There are a couple of things come to mind.
As Will Bark said (and being a mechanic this is sometimes hard to accept) that white looking oil out of the exhaust and hub area IS nothing more than unburned oil. I rebuilt my lower unit twice before learning back in '77; gas was blended differently than the 87 octane today. Which brings me to my next point.
Use only non-ethanol fuel w/ a good 50:1 oil. Where I fish in central MN, the local Holiday station sells 92 octane which is non-ethanol. It helps reduce that unburned oil leaking out after a day of fishing.
If you could borrow a laser temp gun it would be helpful to confirm that the head is running at 140* or 165* after running under load on the lake. When you were told to watch the water flow (I'm assuming from the person you bought the motor from) I'm also going to assume that person may have removed the lower unit and may not have gotten the water tube inserted correctly. Consequently, you would only get some water, not full flow from the water pump to the powerhead. You should have a good flow of water from the exhaust housing port (and the telltale) when you operate the motor at something near mid-range. And the water should be 120* or so, never hot.
Hope this helps;
Kahuner