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Okay folks,
As a teacher, I know that there are no stupid questions... only inquisitive idiots, so here goes:

My engine runs okay at idle and low rpms, however once you open up the throttle it will run smoothly for a minute or less and then the rpms begin to fluctuate, gradually reducing until the stream of profanity from the skipper drowns out the sound of the motor. If I re-prime the bulb, it will run at full throttle again for another minute or so. The tank is vented, the bulb and fuel hose are new. Spark plugs are new. Carbs were recently cleaned and compression is A-okay on all 4 cylinders. But, since an outboard will not run on blue language alone, any suggestions?

Thanks, -K

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How many fuel tanks do you have in the boat?
If you have 2 tanks, do they both produce the same problem?

If you only have one tank, I would borrow and try a different tank in any smaller size like 3 or 6 gallon just to see if it is the fuel tank itself.

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I've been having a simular problem as you are experiencing-- BUY mine is at idle- I just installed a new tank, new hose and an inline filter - You can see that the in line fuel filter is empty and once you reprime it, the engine idles fine-

Have not had time to take the boat out for about a month and I'm going to remove the in line filter and see how it runs

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If pumping the primer bulb while running improves the motor's performance, I say it is a failing fuel pump.

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I agree with Phil. My neighbor down the street has a 1988 90hp Evinrude that was doing the same thing as you describe. We replaced the fuel pump and it works great now.

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Could be the fuel pump, could be a vent clogged or could be carbs. Check the simple things first.

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Second that, and given the age of the engine, wouldn't hurt to check the condition of the fuel lines regardless given what ethanol does to old rubber.