Mainship holding tank vent?

[Alan Mainship]

Have a 2004 mainship 400 and wondering if anyone know if I can drill out the original vent of holding line from the outside. I can see two small holes at bottom half of vent with screen, but can’t seem to get them removed. Can I just drill, possibly a 3/4 “ hole in center to open it up?

I plan to run another vent under anchor locker but would like to leave original for added ventilation.

Thanks in advance for any help.

 

[Dougcole]

You could, I guess, but it might be hard to drill through.

I put a pie plate in the gunnel so I could access the back of the vent, then replaced the vent with a mushroom through hull. Didn't help much, if at all. So I put a new, much larger vent under the anchor locker. That did the trick.

I just disconnected the old vent at the tank and left the hose in place. Getting that old vent hose out would be a real bear.

 

[Bacchus]

You could, I guess, but it might be hard to drill through.

I put a pie plate in the gunnel so I could access the back of the vent, then replaced the vent with a mushroom through hull. Didn't help much, if at all. So I put a new, much larger vent under the anchor locker. That did the trick.

I just disconnected the old vent at the tank and left the hose in place. Getting that old vent hose out would be a real bear.

exactly what I ended up doing last season.
I gave up trying to access the OE vent and have also installed a DIY tank aerator that was fairly easy and very effective even with the old vent.