Ok so not your low hp 454/330 hp deal. You'll get it right. It's always something... Trust me.

This is my last thought on this, Be very careful you did not crack the inner transom plate while torqueing. They are very easy to crack and would exhibit your symptoms. Check very closely for cracks, modifying Ph's diagrams you can check this and also the transom squareness to the stringers. 3-4-5 formula will be very helpful..

Stupid question, you are moving the gimbals bearing to align it with the center line of the engine where it should be on the centerline or are you moving the engine to align with the bar in the gimbal as it happens to be sitting in the transom assembly (TA) and that is giving you your 1 1/2" cant from center line ?

As simple as it sounds, some people that do their own work haven't realized the gimbal bearing functions as a gimbal... (some techs haven't!)

How much movement can you get in the Gimbal with the Alignment bar? ( not putting it into the coupler just moving the bearing?)

On a single I/O the center of the transom / input shaft in directly in line with the prop shaft which is inline with the crank and mounted in line with the keel for straight tracking. To have your rear engine mounts bolted on the inner TA and the engine dictating the true center-line is 1 1/2 inches port or starboard would indicate that the drive/TA is not centered on the transom or the process is off/

the drawings in earlier posts and Glenamy's 3-4-5 are on the money...

A 330 was the original power plant. Spun a bearing a few years back and decided I wanted bigger balls under the hood. I went for a better exhaust system, FW cooling and a new Bravo X. Talk about being over budget. My wife is a very understanding girl!

I agree with the above. Center the engine in the boat and tighten the rear mounts. Install alignment tool into coupler and using a mallet tap up/down left right on end of mallet until alignment tool slides in and out easily. This aligns the gimbal bearing to the engine. Install front mounts and align again.

Let us know what you come up with when you get back at it. You've got some pretty good advice here to move forward. I still can't help but think one side or the other of your inner trans is sucked in tighter. Those measurements will get to the bottom of it quickly. Btw be careful measuring when engine is lifted above you. If you can get it above your deck slip some 2x4's nailed together or whatever you can come up with and lower engine so weight is supported from both above and below. Had a 92 z28 fall on me years ago. Damm near bit it. Something that always stays with me.

Also never share your hobby expenses with YOL. That's almost as bad as using a credit card at the strip club. Lol.

I only found out recently on this forum that a gimbal bearing actually does gimbal. I thought it was in reference to the gimbal housing. I did try using the bearing to get the alignment with the block centered with no luck. The bar doesn't even go in. I installed the drive assembly with an empty engine bed. I used a new TP and took great care tightening up the bolts. No cracks and everything looked good. I have 2 chain hoist front and rear of the engine. the support rigging is overkill so I think I'm ok. I doubt I can get the block above the deck. What is the "3-4-5 method. left right center? I will take diagonal measurements of the mounts. That should show me where I'm at!

It's not easy to hide that kind of money. The truth will set you free!

If you are using the newer style rear mounts , you should be using fiber washer only, no split/ lock washer( double or single) between bell housing and inner t/a. Once rear bolts are installed and tightened (with alignment tool out) , support engine and transfer chain to lifting ring at thermostat housing area (engine centerline) only ( no chain support anywhere else on engine). This lets engine center itself. Lift/lower engine until alignment tool enters coupler ( never use hammer , no matter how tempting) . When alignment feels decent, mark mounts and drill.

I’m certain that it’s only the metal washer and you omit the fiber washer on the new rubber coated transom assembly.

Not to offend or disrespect you and your capabilities but your doing something wrong or missing something. There is no voodoo to engine alignment. Bolt the flywheel housing to the inner plate, install the the alignment tool with the front of the engine hanging. Then set up your front mounts. If you can’t get the tool in the coupler with just the rear mounts in, the inner plate is not square to the outer, the flywheel housing is cocked or the coupler is twisted. Time to start over at step 1