leaking fuel tank

[bleedblue94]

This thread is so hard to make, but I need some suggestions and insight.

A few years ago I rebuilt a 91 Bayliner Capri. Structurally everything I rebuilt is holding up great and the boat is a rock.

During the install I reinstalled the main fuel tank under the deck and added a second fuel tank inside one of the rear jump seats. I don't know the cause or when it started, but the main tank has a SMALL leak it in. I plugged the vent and engine feed lines and put some air to the tank and could hear this ever so slight and frustrating hiss. Once I discovered this I siphoned out the fuel from the main tank and used it via the secondary tank, then once it was empty I just ignored the main tank, and used the secondary tank for the rest of the year.

The boat has been stored for the winter and now that spring is here I am going to unwrap it soon, and I am debating what to do with this situation.

I have a couple options:

*Leave things as is and abandon the main tank and just use the 15g secondary tank exclusively.

*Leave things as is and install another 15g tank in the other rear jump seat.

*Make a cutout with the intentions of putting another ski locker hatch over the main tank, and cut up the main tank through this new ski locker cutout and remove the tank in pieces, then use the area for additional storage.

OR

*Replace the tank in the floor.

This would mean carefully measuring and cutting the deck out right close to the stringers and discarding the deck sections over the main tank. Then coat/treat the inner edges of the newly exposed deck (from the cut) with epoxy, and remove the tank and replace it. I would prefer not to have to redo all the gelcoat on the deck, and I won't be able to color match what is on there now (it was an undocumented mix of blue and green into a teal blue), so I considered possibly making this sort of a complete/all access to the fuel tank for any future issues or needs. I figured I could use some extra white pine that I have or trex decking or starboard and drill holes into the stringers and mount this into the sides of the stringers using 5200 and long stainless steel screws. Then use those piece as something for a starboard deck panel to sit on. my concerns with this idea are many, but my main concern is if putting another hole in the deck between the stringers will cause any sort of structural weakness to the boat as a whole. The last thing I want to do is create a situation where the deck can/will pull itself away from the stringers over time. I may be over thinking this or worrying for no reason, but I want to be sure about this before I do anything since the boat is usable in it's current state.

Suggestions and insight are much appreciated.

I included some pictures from the build to help with the advise, and the link to the build thread is below.

TIA

http://forums.iboats.com/forum/boat...-and-hull-repair/545010-my-1991-capri-rebuild

 

[tpenfield]

The issue I see is leaving a leaky tank in the boat will be a source of fumes and the related explosion hazard. Even though you pumped the fuel out, some remains. It would be best to replace the tank and not use the other tank as the boat should be better balanced.

 

[bleedblue94]

As for balance I purposely put the spare tank on the port side and mounted two batteries on the aft side which seems to hold balance quite well.

If I replace the tank, I need to determine the best way to go about it: replace and glass new floor over it again, or replace and have an access panel...

 

[fhhuber]

I'd have an access panel... and you should see why.

 

[Mikeopsycho]

When my under-deck gas tank leaked, the gasoline odor was impossible to get out of the floatation foam, so for this reason I'd want to open up the deck and see what's happening underneath. As tpenfield pointed out, the residual fuel and fumes could be a hazard. Because my fuel tank extends under the dinette and through the rear cabin bulkhead into the engine compartment I couldn't put an access hatch, but if it's feasible a hatch of a different finish or color than the rest of the deck should look ok. I can't comment on your structural concerns though. Good luck.

 

[Woodonglass]

A stud finder should help you locate and mark the exact stringer locations. Since you installed it you KNOW where the tank is. I'd cut the deck out at the midsection of the stringers and remove/replace or repair the tank. I'd also remove/replace any compromised foam. That IS the correct thing to do. Cosmetics is NOT the important thing here. Safety IS !!!! Dumb Okie Checking Out!!!!

 

[bleedblue94]

I'm not sure where all the concern about cosmetics came from. All I stated is that it would not be possible to color match to the existing deck, so if I cut the floor up I would be curious if an access panel on this sort of boat would lead to a structural weakness, hence the question of if the deck would/could pull away from the stringers.

I see no one has looked at my build thread, bc if they had they wouldn't be commenting on foam. There is no foam located adjacent to, touching, or in the same area as the tank. I used rubber strips to secure the tank and all closed cell flotation foam is in isolated compartments that are not near the fuel.

This comment isn't meant to be rude, but somehow the thread is being derailed with conversation on cosmetics and foam when neither really apply and the main question was based around the premise of cutting the access panel and if the structure of the boat could support or handle having a 48"x20" hole in it without inviting said structural issues.

Wood, this is where I figure your years of experience would be most useful. On larger boats I'm sure large access panels are not an issue, but on a runabout I want to be cautious since I know some rely on the strength of the sole to fortify the overall boat.

You are also correct that if I do cut up the sole I will measure out and cut about 4" from where I believe the stringer is and the work my way closer from there. But would my idea of just attaching starboard to the stringer work? Do you see any issue with it? I'm kicking myself if the rear for not just designing this with a full access when I rebuilt the boat, bc if I had I would have glassed the deck right down into the tank compartment and made the structure like a rock. Now if I plan to do that I need to sand out the gelcoat on the deck and off the stringers in the tank compartment. Obviously something I'm dreading....

 

[Woodonglass]

Ok, If you're ok with everything having been isolated from any leaking fuel and all that's at issue is structural...Then NO, there is NO structural issue at stake. Making an access panel for the fuel tank is perfectly acceptable. I don't think I'd use starboard, but you can if you want. I'd just use plywood and glass and stainless screws with beauty rings to hold it in place I'd oversize drill the holes, use Threaded inserts and epoxy them in place in the stringers, and then Use stainless hardware to hold it in place. If you want more details, I'll be glad to help you.

 

[bleedblue94]

Thanks wood! I always value your experience and information even if I sometimes put my own twist on it ha.

The last thing I wanted was to risk was some sort of shift that would compromise the boat in the long run.

Why would you avoid Starboard? I'm just curious.

Would you make the access panel out of plywood or starboard?

Once I cut the deck, would it be an issue to simply coat the exposed cuts of wood on the deck (the cut sides of it) with epoxy? or will I need to use csm as well? I don't want to risk the deck rotting, but I don't want to have to sand away all the gelcoat to give the epoxy a place to grab and then have to gelcoat everything again.

Thanks again!

 

[Woodonglass]

Gelcoat and epoxy to play well together. If you're gunna gelcoat then you're gunna have to use Poly. Starboard don't like things sticking to it. Not poly not epoxy not much of anything.

StarBoard can not be glued using standard adhesives. Products like 3M's 5200 work well as a water sealing caulk but will not adhere StarBoard to itself or other materials in a permanent bond. It is preferable to mechanically fasten StarBoard but when an adhesive is necessary you can use a product called #7540-AB or 3M's Scotch-Weld DP-8005. We do not represent these products, make any claims about their abilities or accept liability for them. We have however used them with success and had good response from others who have used them.

Sooo...once you get the deck cut out you'll need to soak the exposed edges with resin and then tear some CSM (make it Hairy) and layer it on the edges to seal em. Then cut the plywood hatch to fit and Coat it with resin and Glass and then Gelcoat it. If it were me I try and devise a rubber seal or sorts and then use stainless screws to put it in place. Hope this all makes "Visual Sense"

 

[bleedblue94]

SO good news:

This may have been a combination of bad circumstances:

have a compartment that I store my 2 stroke oil mixing supplies and that compartment has a drain that eventually dumps into the bilge. Before going crazy and tearing the deck up I decided to do one more test on the tank in place, and found that the main hiss I heard was actually from the combo fuel fill/vent hissing out to the atmosphere under pressure, BUT I still heard a slight hiss inside the bilge. So slight I had a lot of trouble locating it and finally think I found it coming from the vent fitting on the tank. I only am at this conclusion bc I could heard a pitch change in the hiss when I pushed or pulled on the fitting. Great news if true, BUT the hose barb elbow appears to be frozen in the fitting now.

Any suggestions on how to free it in this tight area? I don't want to try to break it free and damage the threaded portion in/on the tank in the process. The other question is whether there is a good sealant I could just smear around the threads where the elbow bard threads into the tank as things are rather than trying to wrestle the fittings apart?

Thanks!

 

[tpenfield]

I would do the 'soapy water test' to verify where the air/hiss noise is coming from. Spray a bit of soapy water around where you think the leak is coming from and look for bubbles to form as you pressurize the tank. While you are at it, check the other fittings on the tank as well.

Keep in mind that the tanks are generally rated for only about 3 psi.

If it is the vent fitting, it may be corroded, which would probably warrant pulling the tank and giving it a full inspection.

where you able to see if the tank is foamed in or just strapped in?

 

[bleedblue94]

I just rebuilt the entire boat 3 years ago. It is neither strapped nor foamed. The compartment was built to the proper size and used fresco's idea with the rubber mat strips for support and spacing to let water drain. It is not an aluminum tank, it's poly, so it's not corroded...

I am 99% sure the leak is from where the barb elbow threads into the fitting on the poly tank.