Fuel tank ventilation

What are the symptoms of a outboard running with the vent on the tank closed, or partially closed?

Thanks

You run out of gas. The vent needs to be open when the engine is running.

At first, the priming bulb sucks down flat, while the motor needs more and more throttle, than the motor gets "real quiet".
Tim

Great. I may have other issues then. I thought it might be causing a bad bog i had Sunday. We started fine for 20 minutes or so. Got it up to 23 mph. Then the motor fell flat on it's face. It would not get over headway speed. It shut down twice, but restarted with one pull each time. After restart it would get right up to 16 mph, then start bogging down, and would not get over 6 mph. Someone said it might be a bad fuel oil mix, and that the motor was limping back so not to cause damage. Once I got the boat back on the trailer, I checked the vent and it was almost closed. It just won't rev without going into a stall til I let off on the throttle. It idles fine, and goes into gear with no issues, unless it was under load and moving. In neutral it reved up but I could feel it was not as it should be. Lower end is fine.

Any thoughts? This just came on all of a sudden, and only temporarily came out of it during restarts, then started bogging again.

Did you check the primer bulb and see if it got soft when the problem happened? It might not be getting enough fuel. That is the first thing I would check. Run the boat and when it starts to fall off see if you can pump the bulb.

I actually did check the ball. It was soft, and would not pump to firm. I was trying to pump it to see if it was not getting fuel. That was a big ding ding ding for me, but I was nervous about making it back, and never checked the vent til I had it on the trailer.