Searched around and gave up.[&:]

Zen 230 gas weedy:
Engine will be inverted to keep CG low as possible. Tank placement: up high in line with the engine or can it be deck mounted?

with gass engines you can mount the tank (depending on how good your carby is) up to 3ft down from the engine.

so yes it can be deck mounted.

if you tanke the carb off you will see that there is a large hole with a butterfly valve and to smaller holes about 1.5mm in size.
these are called pulse holes and they take some of the crank cases pulse to drive a small diaphragm whick pumps fuel from the tank into the carby and then to the jets.

this is only a short explanation.

but in summary YES you CAN deck mount the fuel tank.

shaun

Shaun,
That was a simple & very informative answer. Thank you.

My airboat is starting this weekend. New band-saw, new engine, new friends & new fun.