Thanks, but my cap is not vented. It builds up pressure or goes into a partial vacuum, based on the external temperature. I have only used my engine in the marina. I imagine it was under pressure at that time. Also, it has leaked gasoline in the well while sitting at the marina. I loosed the cap, and no longer have that problem.
I seem to have captured water in the tank now; I guess from the humidity. I ran about 10 knots for a few hours to go to an island, and after stopping at anchor, my engine wouldn't run past idle speed, though it did shift into neutral and reverse. There was no wind the next morning, and I was planning on having another boat tow me. But as I was moving to another anchor, it started running right. After I got within a mile of port, I emptied the ballast tank and ran my engine on high for about 20 minutes.
Several months ago, I sent a text to Blue Water asking about a vent, and the engineer said that nobody has complained about that.
I guess I need to get a different cap. I would hate to either rupture or collapse the tank. Do the new gas caps only event into the tank, or will they also vent from the tank?
Thanks for your input.