Gas tanks that dont breathe need help???

[Marco]

I have an old 1998 rig/ 200 Vmax, i have this probleme since 2 years. When i run for more than 1/2 hour the tank i used starts deforming (shrinking) and the motor stops. I have to open the gas cap to put some air in the tank to can star back the motor. The onely thing i can see is i lost my O'ring arround the gas cap? I think the tanks breathe by the gas cap but i'm not sure?

Is it the o'ring or should i bought new gas cap? or else??

Thanks for any help

Marco

[BASSIN2971]

The vent is blocked and will cause powerhead failure quickly if the problem is not resolved. Check your vent line for droops in it were fuel could block off and check the cap for debris in the vent valve area. worst case change the cap to a none vented and add a vent on the side of the boat. We have done this a few times due to water sucking in the vent when coming off plane