Condensation on the underside of the deck over fuel tank

[TIPGrady]

Hello,

I just bought my first Grady, a 1992 Tournament 190 with a 1992 Yamaha 150. The boat has been sitting for a while and I wasn't sure what was in the fuel tank, so I decided to pull up the deck and check things out. When I did this, I found that the underside of the deck panel was covered in condensation. It didn't seem like only water, as it was kind of viscous and slimy. There was also quite a bit of this on the top of the tank. Is this anything anyone else has experienced? Does it hurt anything? If so, what can I do to prevent it?

Thanks for the help!

 

[Hookup1]

Decks

Clean evertyhing up, put it back together and caulk. Remove the round access port(s) from the deck, clean up and re-caulk. Pop the access port insert out, clean up, install a new O-ring with grease. These port leak!

Use it for a few weeks and pop the access port and see what you have. Should be dry.

 

[choogenboom]

Both my Gradys had similar moisture and growth - its black mold. I have not proven conclusively its leaking deck plates but pretty sure Hookup1's advice is right on the money. What I have noticed is the mold is concentrated on the area beneath the deck plate and dissipates within 6 inches of the deck plate.

 

[seasick]

On my 208, the tank space is 'open' to the bilge. If I run water into the tank area, it finds its way to the bilge. Therefore, any moisture in the bilge is also exposed to the tank area and we all know that the bilge is always moist.
When the boat is in the sun and during the warmer daytime, the tank, the fuel and the fiberglass itself store heat. In the cooler hours, the deck starts to cool and the warm air underneath condenses on the underside of the deck. Cooler air in the bilge also causes condensation on warmer surfaces. Moisture buildup in inevitable. Only ventilation will help and that isn't always practical. You can stop/slowdown water infiltration but you will never stop condensation unless you live where the hunidity is very low. (think Fairbanks).
If the moisture problem is not excessive, adding a desicant product may help.

 

[NIGHTIDES]

Re: Decks

Clean evertyhing up, put it back together and caulk. Remove the round access port(s) from the deck, clean up and re-caulk. Pop the access port insert out, clean up, install a new O-ring with grease. These port leak!

Use it for a few weeks and pop the access port and see what you have. Should be dry.

Hookup is on the money..

But what I did instead of greasing the access port + o ring, I chalked it shut. How often to you go poking a look in there anyway..?? A quick slice w/ a blade will break the seal if and when I need to look in there..

Keeping thing super dry is what I am after.

Good luck.

 

[HMBJack]

I have a full cover on my boat. After the wash down and the cover is on her, I typically open all of the inspection ports to let everything breath. This, I have found, eliminates any kind of moisture trapped in the fule tank compartment. Only take a couple minutes to remove or replace.

 

[TIPGrady]

Thanks for all the advice. I am going to re-caulk everything and get some o-rings for the access ports. I discovered that there aren't any o-rings right now, so I'm sure the ports have been leaking. The good news is that I have left the deck off the last few days and everything has dried out nicely. Is there a specific type of caulk that everyone recommends for this application? There was clear silicone around the deck panel before, but I wasn't sure if that is the best to use.

Thanks again!

 

[NIGHTIDES]

LIFE SEAL...excellent stuff.

 

[Hookup1]

Order the O-rings from McMaster.com but check you size. These are what I ordered for my '97 Islander.

McMaster.com p/n 9452K516 Their are 5 in a package. $4 but with shipping it will cost you $10. Buy them locally at your own risk!

By the way, you probably will never get this compartment totally dry but you must keep the sea water off the fuel tanks! I caulked my plates with fast setting 5200 or the LifeSeal equiv. These products are polyurathane and have adhesive properties in addition to sealing.

NOTE!!!! Just to clarify, I caulk the deck plate outer ring to the deck and install new rubber O-rings on the inserts with a little silicone lube (no caulk).

For the deck I used a high quality silicone bath and tub sealant from Home Depot. The silicone is easier to remove the next time you need to take the deck up. Scrape most of the caulk is off and wipe down with lacqur thinner. Use masking tape to tape out the edges and re-caulk. Squirt plenty of caulk in the gap to fill it.

Good luck!

 

[GWcpa]

I have a full cover on my boat. After the wash down and the cover is on her, I typically open all of the inspection ports to let everything breath. This, I have found, eliminates any kind of moisture trapped in the fule tank compartment. Only take a couple minutes to remove or replace.

That's what I do. My tank area stays dry. I wash any grit off the O rings and lube them.

 

[Curmudgeon]

I caulked my plates with fast setting 5200 or the LifeSeal equiv.

You'll know why 5200 is a bad idea when (NO IF) you have to replace 'em. Try GE Silicone II for the entire job, all will be sealed just fine, and you can get 'em loose the next time you need to ... :wink:

 

[seasick]

I pop my access covers a few times a season to check for fuel leaks and to check fittings. I personally wouldnt'y caulk my access plates