I have recently purchased a used MT-7-235 and this is the first time operating a Maule.
When I refuel, I cannot fill the 4 fuel fuel tanks to anymore than approximately one inch below full, without fuel overflowing. Is this normal as previous aircraft such as a Cessna could be filled to the top? Is this normal and how do you deal with this situation without wasting fuel, apart from not filling up? I have a colleague with an M-7-235 and he has experienced the same difficulty.

It's normal for a Maule. You can buy a check valve kit for each tank from Maule that improves the situation but they're pricey. Maule tells owners to fill no more than 2 inches from the top to avoid siphoning out the vent tube. While on the ground, put the fuel selector switch in right or left but not both. That will prevent a wing that is higher from draining into the lower wing through the fuel selector and causing it to siphon out.

I have an MXT7-180 and found that if you fill the main tanks to about 1/2 inch BELOW the BOTTOM of the FILLER NECK the fuel won't drain out the vent. As you taxi out, run each tank for a couple minutes and you should be good to go. As Andy said, make sure the selector is on either LT or RT. Don't park it in Both or OFF....
Mike

2 things I found help a bit with the vent overflow: 1: Install the check valves. They don’t work 100% but they help. 2) Make sure the vent line bends up as far as it can where it exits the tank. The idea is to keep the siphoning from starting. Again, that helps but not a 100% solution.

So when I end up with the vent dumping a steady stream of hard earned avgas all over someone’s pristine environment, I deploy my last line of defense. I keep 2 sections of automotive fuel hose, each about 10” long, one 1/4” ID the other 3/8” ID joined together with an adapter fitting. Kink the hose then slip one end over the offending vent. Be sure to block off the small hole on the back side of the vent. Then release the kinked hose and blow through it to purge the line. Remove the line and see if it worked, usually does on the first try.

The 3/8” (main) and 1/4”(aux) sizes work for the M5. Fairly sure other models are the same.

Kirk

When filling all four tanks, remember dihedral, the aux tanks are higher than the inboard tanks and if you have the single vent system, fuel will flow from aux across the T junction which has a check valve below it, and into the main thus overflowing the main. That excess fuel will seep out the vent on main fuel cap and flow down rearward and inboard on top wing skin. If you don't have proper tape seal under the wing root top fairing the fuel can enter and stain the headliner.
So, do not overfill the aux tanks. Remember that fuel from underground tank is usually cooler than ambient and when placed in the wing tanks that fluid has some expansion.

Thanks for the information above. All very helpful.
Andy, if I fill each tank to 2” below top, do I still get 70 gallons of fuel capacity with the 4 tanks?

I flight plan for 66 gallons with fuel in all four tanks.