Testing fuel tank
 

I have a 1990 Formula 242ss and sometimes I notice some gas fumes in the cabin. Can someone tell me the best way to test the tank in the boat? Pressurize the tank? See if it holds pressure? If so how much pressure? Thanks for any help

3 lbs pressure

If your going to pressure test it remove the fuel from the tank first.

Is there an option other than pressure I was thinking about smoking the fuel system

do not pressurize the tank. 3 psi doesn't sound like a lot but multiply the top area of the tank by the 3 psi and see how high the side force is.

Pressurizing the tank won't work. Most are vented to allow for thermal expansion and prevent condensation.

Hydrostatic- plug vent and outlets, fill the tank until liquid is at the top of fill tube and wait...if it goes down leak

check your vent lines too they could be cracked and allowing fumes to escape

You can pretty much bet on the tank needing replacement. It's 27 years old and, most likely, unfinished aluminum. Not trying to bust your chops, but that's going to be the case.

I have a 1977 boat and when I had it apart for stringers I decided to go ahead and replace the tank. It was corroded badly on the sides and bottom and ready to start leaking. Glad I pulled it.

700 bucks and three weeks time and I had a new tank at the door. I bought mine from Florida marine tanks.

Most tanks have a tag on them to let you know how high to test them mine are 5psi in my boat. But all tanks are different.

Can you get to your tank easy? Drill some core holes in front and back of the tank and smell the foam. Don't drill through the bottom.

I bet some air will trapped in the tank that way. Also the temp will have to stay the same the whole time you are testing.

They make a dye that you can put in your fuel that is traced with a simple UV flashlight. I don't know if it'll work for your situation but it made it easy to spot a single drop of oil from yards away. $10 at any auto parts store.

I had a similar issue on my Pantera. I had owned it for 3-4 years. First I checked the vent hoses. Then I pulled the entire cockpit interior and floor to inspect the tank.
Couldn't find anything. Finally, I checked the fuel fill. The clamps that held the hose to fuel fill were both loose as chit and the hose had loosened up with all the vibration over the years that fumes were getting into the cabin.

I agree, it happened to me on my 1992 Checkmate about 5 years ago. Noticed the fumes and then small amounts of fuel dripping from the drain plug hole while on the trailer. Luckily it was winter and I had time to replace it. The tank was unfinished aluminum and badly corroded on the bottom where it was foamed in. Not a fun job to replace.

One other thing. Two years after changing the tank I noticed fumes again in the bilge, especially after filling up. It turned out ethanol destroyed the gasket for the fuel sending unit on top of the new tank. That was an easy fix and something else for you to check.