once apon a time i had a Dumas Large Swamp Buggy - needless to say i had a few issues with it the main one being that it always seemed to pull one direction and would not track straight.[ the hull was warped] so it was torn apart and rebuilt and now the hull is straight but i still cant get it to track straight, it pulls to the right, i can give it full left rudder and it tracks better but still not straight ahead. my only thought is that it is in some way unbalanced, perhaps the muffler? but sitting in the water it looks like it's vertical and not listing. any help, ideas, questions or comments would be welcome.

In my opinion....

If the motor was sitting further back toward the transom it would help alot.

If the hull is symetrical I would have to think that maybe the motor stand isn't sitting square
on the boat? Have you double checked?

it could be the wind resistance against the muffler , if so you need to even it up on the other side
with something of equal size looking from the front.

Wind resistance MAY be a small part in what you are experiencing.

Torque induced turn is more likely the cause.

If you are able, try pointing the front of the engine a few degrees to the left (since it it turning right). This should counteract the torque and get it to run straight.

All my hulls are set-up so the engine starts out positioned on a neutral plane. ( zero degrees up/down as well as left/right in relation to the hull bottom) I then shim the engine in the pylon during the first several test runs to get it to run flat and track straight.

And as dadaddyro stated, it would also help if the engine were located a few inches further towards the transom. By the looks of the side view pic, the prop centerline is slightly forward of the hulls centerline. (it's that whole physics thing again) This could be cause for difficulty in steering on this type hull.

Alone with what has already been said, check the trueness of the hull. If you was to sit the hull on a flat surface,(table saw table works well) does it sit flat, or can you push down on one conner and the other comes up? Take a measurement between the sponsons Farward to rear, are they the same?
Like what was said check the engine alinement. Use some type of striaght edge, place it on the side of the mounting plate of the engine, then eye ball it down the sponsons.
One more thing that could maybe cause this, It looks like the engine is facing down. With the tourqe of the engine + the engine facing down=one sponson having more friction. Making it track sideways or even turning. Kinda like having a break on one side.

thanks for all the ideas, when (if-i've got a hell of a schedule) i get it back out to the lake i'll let you know what happens hopefully somthing for the better

AND ....( had to throw in my peniies worth )
Are the sponsons evenly apart ? meaning , are they same distance front to rear and also , are they 90 degree's to the belly and motor ?
( possible that maybe one sponson is not trued ? )

Didn't think of that one....[X(]

I guess that vacation cleared the mind a little....