Ventilation cap

[Boat of Us]

Hello all<br /><br />My motor is a Evinrude 100hp 1989. I presume that my fuel tanks date back to the 80's also.<br /><br />My question is about the caps. There is no vent screw on top of the cap. When I crack the cap, I here a swooch.... is that normal? <br />I guess that means there is air in the tank. <br />The bulb isn't hard but seems to have a flow when I pump.<br /><br />Can someone explain to me how all this should work.<br /><br />Thanks

 

[JB]

Re: Ventilation cap

What kind of tanks are you using?

 

[seahorse5]

Re: Ventilation cap

If you are using the metal or plastic 6 gallon genuine OMC tanks, they are vented for vacuum, but not for pressure. That way, as pressure builds up from warm temperatures, the gas fumes will not escape out to settle in the bilge and cause an explosive condition in your boat.<br /><br />They are vented for vacuum so they allow air into the tank to replace the volume of gas consumed.

 

[Boat of Us]

Re: Ventilation cap

I am using OMC metal tanks from the late 80's.<br /><br />Since I didn't have a cap with no vent screw, every so often I would crack the cap to let out the air. A few weeks ago, I was on the lake for a few hours and just before getting back to the marina I accelerated. By doing that the motor wanted to die,and the bulb had no pressure in it. Do you think that happened because I let the air out?<br />I went out last week-end and everything was fine.<br /><br />Thanks again

 

[ED21]

Re: Ventilation cap

Those OMC tanks have a vent that is opened when you plug the hose into the tank. The spring pin on the tank fitting opens it.<br />I would start by checking the fuel filter & pump diaphram. Changing out the bulb is an easy fix & then you have a spare if is OK. Sometomes the O rings on the fittings wear out & let in air. They can be replaced.