I owned a Valco flat bottom boat and it had a 115 jet on it, no tunnel and went all over the place and never had a problem. That was before any forums or tunnels,
I now have a Woolridge with a small tunnel just big enough to smooth the water to the jet foot. With the jack plate I can fine tune the jet for the load and change out for a prop for lakes and ocean.

I don't know that specific rig. I would assume they paired it to run well but probably not fine tuned, maybe the dealer did. That would be the question for me, was the dealer familiar enough with jets to set it up right or at least the original owner.
Next would be condition of the pump and impeller. Pull the grate and eyeball the impeller are the edges chewed up, check the clearance, check the bearings. This is the heart of the foot if has been sharpened and reset fine but has been done till there's no more life left. Next I'd look at the linkage for the clamshell. Not as prone to wear but it is exposed and can sustain damage.
Back to the rig, I wouldn't worry to much about misalignment unless it's obviously off. The leading edge of the grate should tuck just above the bottom of the hull. The main thing is it should not hang down below where it can get caught. Next check the hull. The transom weld should be smooth and perfectly flat to allow water to flow as one flat sheet to the grate.

We had some of the early tunnels back in '93. The tunnels were too wide. The boat squatted too much. Never hit the foot of the jet. Destroyed the back of the boats. Had boat plugs on both sides of the tunnel. They were destroyed first.

FYI That G3 probably has a the high transom and a short shaft jet. Pretty sure you will not be able to convert to a prop. The transom is too high for a short shaft prop. if you can find one.

Hovercraft
Dennis

How long does it take u to switch out the jet to the prop?

Couple of hours.
This is a early 90's tunnel on a Woolridge. Approximate size 16" wide X 12 inch taper.

I have the g3 1548 vbw with a 40/28 Johnson jet runs good as long as you don't overload it . I've run this setup shallower than I should.

I am more than willing to sacrifice fuel efficiency for the ability to run through shallow water. I have a Yamaha 70 jet and a 30/40 Evinrude. As long as you don't back off the throttle you can run through very shallow water. Without a jet you simply can't get through a lot of areas on the Allegheny River. I can't imagine having trouble in a foot of water!

I have a catfishing buddy who is a pretty big dude. Once we get all our crap in the boat for an all nighter, will this thing move along ok?

How big a ole boy are ya?

The thing with jets is not only do you lose about a third of hp at the pump but they dont have the torque of a prop but for running shallow rocky rivers they are hard to beat just go as big as you can far as hp.

Haha im not huge-225. My buddy has gastric bypass and is now around 280. When he was 440 he sat down a little quick one day in my old 16 footer and i did a back flip over the side into the river.

I'm around 250 and my dad is probably 220 it does pretty decent for us I would like to have a 60/40 or bigger, of course that means a bigger boat and that all means $$$$.