Fuel tank inspection port

[John Reid]

Gorden,My 20-year-old boat has a 40 gallon aluminum fuel tank, and I think I can accurately say it's got some crud in it. (When I'm out sailing in a steep chop and the fuel gets slushed around, I can count on having to change my Racor and Yanmar secondary soon.)Access to the tank is great; it's right under the aft cabin berth. But there's no inspection port for opening it up and cleaning it out.My questions are: 1) Does an inspection port make sense (seems like it, but maybe I'm missing something) and, if so, 2) does anyone make / sell a prefab inspection port (flange and cover).I've been told not to put a plastic inspection port in the tank since it's fuel and also because diesel makes plastic brittle.I've looked for a metal version, but no luck. So I thought I'd ask the expert.Thanks,John Reid

 

[Gordon Torresen]

Aluminum inspection port

I know ofno ready made inspection ports. What we usually do is make a plate of material similar to that used for yout tank, locate it on top of the tank (watch out for baffles) and drill a series of holes about a half inch in from the edge through the plate and the tank top. The drill should be a tap drill size. Now you remove the plate and open its holes for screw clearance. Tap the holes in the top of the tank and then cut the hand hole about half inch inside the holes in the tank top.We find that the hand hole should be 5" at a minimum to fit a fist. You then cut a neoprene gasket (1/8"), transfer the holes and screw the cover on with stainless screws.  Since you are cutting the hole to clean the tank, you are not overly concerned where the chips may fall, although its a lot neater if you have a vacuum cleaner suction hose next to your drill bit. So much for putting your hand in the tank. Usually the crud that you want to remove is in the water at the bottom of the tank. It is below the lowest reaches of the fuel pickup tube while the boat sits flat. You can get to the crud through any opening on the top of the tank, it doesn't have to be big. If you have a fuel gauge sender there is plenty of room. If there is a pipe plug or the pickup tube in the top of the tank, that hole can be utilized. Get the water and crud to the lowest part of the tank and go in with a stiff tube and pump it out. A little oil change pump is great to use. You are only after a small amount of water. Keep in mind that the lowest part of the tank can be moved around by pulling on a halyard (watch out for waves). We like to do it in a travel lift where we can have better control and give the crud more time to move down.

 

[Sam Lust]

Another take on inspection port

I did the inspection port on the 20 gallon aluminum tank in my 33 a little differently. I was able to get the tank out with a minimum of cutting. Only an inch off the fill barb -- not anything to worry about. I cut a 6 inch hole in a spot where the space was available and would enable me to peer in once the tank was back in place. The cover itself is 1/2 inch thick Lexan Polycarbonate. Now here's where it gets a little tricky, and I display my typical overkill. I used 12 1/4-20 bolts to secure the cover, but rather than relying on threads cut into the fairly thin gage aluminum to hold the plate, I threaded the bolts in from the inside, leaving what are in effect "studs" sticking out from the surface of the tank. I used Permatex blue form-a-gasket. I discovered a tiny bit goes a long way. Plain nuts over flat washers (all hardware is stainless) completes it. Pull down all the nuts in a rotating pattern and it's done.The point here is, among other things that, after that many years, in my case about 16, there is bound to be a good solid layer of munge. I had a 3/4" layer of nasty garbage and discolored slime on the walls. As I got the boat from the previous owner the tank was filled with 8 gallons of black fuel, 8 gallons of water, and a gallon or 2 of black goo. I scrubbed it out with everything I could think of, rinsed thoroughly with water and sun dried for hours.I have no leaks from the inspection plate, and no more problems with bacterial growth or water blocking my filters and stopping my engine, and I can get a good idea of the condition of the interior of the tank. Just to complicate matters, I made up a new fuel pickup tube which goes through the new plate and picks up fuel from dead center instead of all the way to one side. Less worry about sucking air when the power boats wake and roll me while I'm under power at the mouth of our river. But that's a subject for a whole different post.