Inaccessible Leaky Observation Plate on Fuel Tank, need some advice.


Staff member
Dec 22, 2018
Midcoast Maine
Learned Colleagues

I've got a aluminum plate that's screwed into my fuel tank covering a hole. The hole serves absolutely no purpose and "may" be leaking a little. I got a replacement gasket, but there's NFW I can get to all the screws holding it in. I did cautiously tighten all the screws, but really didn't torque down hard, afraid of pulling out the mollies in the plastic tank. Now while this was "leaking" the fuel gauge sender was leaking and that has been replaced. Not sure if the gas by this port was from itself or from the sender because it's "downhill" from the sender and fuel from there could pool around this plate. I never tested things after fixing the sender I've kept the tank at 3/4 or less fill which didn't have any leaking anywhere.

So I have 2 options:

  1. Cut a hole in the deck and put a new access port in over this plate so I can easily access it and replace the gasket. I don't like this idea as I never like cutting holes in the deck.

  2. If someone can suggest a "caulking" solution that would work in a plastic/aluminum/rubber environment. The area is free of fuel (gas). If necessary, I want this "caulk" to be removable in case I do have to go full tilt and cut the deck, so my initial idea of 3M 5200 is NOT appropriate.
OK, who's got some ideas??

Thanks - R7


Jan 17, 2019
Try a small test with something like JB weld,rough everything up with sandpaper if you can and clean with a good solvent.
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Feb 13, 2019
I had a similar problem on my Hydrasports Seahorse 230 WA. Like you, I was not happy about cuttingt the deck. But in the end, I thought, "God hates a coward" and got out the jigsaw. The deck was glass with a wood core. The glass did dull out several saw blades. But overall the job was quite simple. Just make sure of two things. 1) Measure carefully that you're cutting in the right place, and 2) make sure there's enough clearance between the deck and the tank and any hoses (don't want to cut through either of those. Also, when installing the new deck plate over the hole you just cut, make sure you use lots of caulking. You don't need rainwater leaking into the bilge. Really it's an easy job and once done, you're good to go next time you need to get in there.

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