Condensation dripping on fuel tank fittings

[IFish4Tuna]

I have a 1999 Bimini 306. When ever I pop off the cover of the access holes above the fuel tanks I find they are wet on the inside cover with condensation build up - all summer & fall.. Also it drips top of the tank. There is always a puddle on top of the tank around the fittings both front and rear tanks. I resealed the fittings last year so its not leaking around the mounting area. Also fresh o-rings. These are pop-top fixtures.

Looking for other people's experience on this. Is that just the nature of the pop-top port hole fixtures. It's made me wonder if I have excessive moisture where the fuel tanks are.

So I bought an endoscope on amazon for $30 and ran it down the rear of the rear tank to the lower deck that the tanks sit on. I did not see any puddles. BTW the endoscope works awesome for $30 (records and takes photos and has a light). Did same on the front side on the front tank. No puddles down below. Wondering if there is just enough condensation build up from the aluminum tanks to draw moisture from the bilge area.

I also reached inside the access hole and felt around on the underside of the deck and did feel some moisture in a few areas. The water on top of the tank is localize to the port hole areas despite some areas being moist on the underside of the deck. Also not sure if that's condensation or if the the center floor panel may need to be pulled up and rebuilt.

Anyway I really am trying to avoid standing water on top of the fuel tank fittings. Any advice welcome on experiences w/ this.

 

[Hookup1]

It's not all condensation. The pie plate access ports are leaking. If liquid is discolored it's probably a rotted deck panel (leaking coffee colored water from deck core). Pull the ports out and caulk them in with 3M4000. Then replace the o-rings. Use a good grease on the o-rings. I also put a piece of 10-mil plastic over the tank sending unit under the port. This photo is of my deck panel that I rebuilt with Coosa board coring. Tanks were replaced later.



Beckson Deck Plate o-rings
These were sized off new Beckson deck plate.
www.McMaster.com
9452K515 Dash number 359 $8.66/5-pack 3/16" x 5 3/4" x 6 1/8" - OEM size.
9452K514 Dash number 358 $8.30/5-pack 3/16" x 5 5/8" x 6" - One size smaller - plates go in and out better. My choice.

Harbor Freight Super Lube 3 oz. clear synthetic grease $8.99

 

[Sardinia306Canyon]

My 2011 Canyon does the same as almost all other boats on the market to that when the round access plates start to leak.
The one over the fuel tank sender and elbows is the most obvious one as the water make a poodle there and i still don't understand why tank manufacturers doen't make the tank top a tiny bit curved so that water flow away and don't poodle there.
However, there way be also condensation from humidity condensing on the cooler tank outside but thats not really concerning for the tank, while the poodle around the fuel sender area is concerning.
My bilge is bone dry even if she is in a slip and i did not noticed obvious condensation, if you are sure that the tanks have condensation on their walls then you may leave the access plates open if on a trailer or check if you can get your bilge dryer.

As Hookup1 wrote, replace the round access plates with new ones, caulk them correctly and use a thin film of silicon grease after you removed them and reinstall them again. The silicone grease is not a sealant, but it will reduce wear on the o-ring.

Chris