Fuel System Troubleshooting

[JOHN COOKSON]

. Now I will have to find the clog in the line to fix the problem for good. If there are any suggestions for the best way to do that on an older Cat 30, it would be appreciated.

When this happened on my Catalina 27 I ripped the whole vent system out tank->transom and then replace the vent fitting in the transom and ran a new ethanol rated hose tank-> vent fitting. I wanted to be sure any ethanol fumes would not rot out the new hose.
Maybe on your boat ethanol has rotted out the hose so much it has collapsed.
On my boat the vent was blocked because a small screen in the transom fitting corroded and became blocked. I inspect the new fitting yearly with a mirror.
TRUE GRIT

[sastanley]

Ah...OK...look for a sag in the vent just aft of the tank under the quarterberth..I taped mine up to the quarterberth opening to get it to stop sagging, and cut it a little shorter to help discourage the tendency to sag...it is probably pretty old stuff..mine was red and chalky. It exits up and thru the stbd side floor of the lazarette and out the transom on my boat. It should take a similar path to the larger (passive) side of the blower system hose in the same area. I eliminated my long vent run when I went to a new fuel fill with an integrated vent last year after realizing all the water coming down the side decks was going in the fuel fill with a bad o-ring.

It sounds like yours is still sealing given the situation you are describing!

I might also replace the hose..if you have to remove it to clean it, replace it! If it only has fuel in it (maybe), it might run back in the tank after the sag is eliminated.