2001 Grand Alaskan sea trial vibration issue..thoughts?

Didn’t want to side track the thread so I deleted my post asking if it was Yolanda. She's good people. Someone you can trust.

A related thread: Hatteras vs. Grand Alaskan...
https://www.yachtforums.com/threads/hatteras-75-vs-grand-alaskan-78-2003.29909/#post-259089

Usually the cutlass bearings. May look ok if only moving prop manually but should always be done with a long 2x4 board or larger pried on ground beneath prop and used as a pry bar. There should be no movement in cutlass.

If you get a satisfactory answer to why the rudder is bent and why shafts and wheels were replaced you could then go to next steps. Ask the seller to check some of the easier, less expensive potential causes of vibration to see if it is an easy fix or more involved. Given the extent of vibration explained, the seller should be willing to have the engine alignments checked, the cutlass bearings properly inspected and the motor mounts looked at. Assuming the shafts and props are good due to recent replacement, if alignments, bearings and mounts all check good then there is an issue that is likely to get much more expensive and involved to correct.

Regarding vibration - It's not clear to me if vibration is related to RPM speed, or vessel speed through the water.
Does stopping/reducing power on 1 shaft; while leaving the other WOT, change vibration immediately, or when vessel slows down? And finally, THAT RUDDER! It's not just bent - it's curved. So it's creating "lift" which is creating cavitation.

I'm aware of fins creating some problems like "fishtailing" on a straight course, to the point of needing to relocate them, but I never heard of vibrations.
That's good news anyway, if nothing else because checking if they are really the culprit is very easy:
Just pull them off (which is a reasonably easy/fast job) and see what happens.
Pretty sure their shaft alone can not create a drag relevant enough to transmit any vibrations.

PS: I am assuming that you already tried to run the boat with the fins center locked - if not, it would make sense to try that first, obviously!

Lots of good ideas here. To summarize easiest to hardest in my mind. This might just be good ideas for anyone reading this who comes across a vibration and heads back to the dock before checking further.
Run the engines up to speed in neutral one at a time and then both.
Run the boat with the stabilizers centered and depending on the style a second time with them turned off and free flowing. They could be misaligned so they think they are centered and really creating drag/disturbing the water.
Run the boat on one engine and then the other to isolate if it stays with a side.

Then back at the dock schedule someone to look at alignment.
Throw on the bathing suit and check the props for lines or severe damage to the props.
Assuming hauling takes time and money that's the next place I go. Checking props out of the water to make sure a blade isn't forward or backwards a bit, the edges are smooth, cutlass bearings, shafts turn true, etc.
Then pulling off props for reconditioning, pulling shafts, etc.
Then calling someone who specializes in vibrations.

However, for a potential buyer, nothing has changed. The boat's got a significant issue of unknown cause. Might be minor or might be major. I'd put the burden on the seller.

Considering that the seller must be aware of this issue, you would be better off stepping back & working out why the problem was not addressed by the owner before putting such a vessel to market. Whether it is a Grand Alaskan or Grand Banks or Fleming; fact is there is an issue which is serious & has not been resolved by the owner who wishes to sell the boat. I would step back & suggest that the owner resolves the problem before you go through with the purchase. Why would you go ahead & buy into a problem that is not yours? Given that the market is so strong it may be a case where the seller is trying to offload the boat knowing that the problem is difficult to resolve, or costly & hopes that the buyer will compromise.
In any case, you have the choice to say no & move on to find a vessel without these problems, even in a sellers market. Do not put yourself under pressure to buy an obviously attractive boat, but one with problems that may be serious.
Keep in mind; every major issue will mean time where you cannot use the boat. You may be spending months with the vessel on the hard stand. Plus the cost. Do not compromise.

A lot of the Taiwanese tubs have vibration and ill handling characteristics when you push them past hull speed. A cheap build is a cheap product with poor engineering. That and your rudder is clearly bent in the 4th picture. I would run and buy a quality build.

Just don't ever take on someone else's problem unless you're sure you know the solution.

adding my 2cents.......although a well laid out yacht and may fit your needs......i would not walk away from the deal i would RUN

patience is a virtue and good comes to those who do their research not always in a hurry.....plenty of fish in the seas and nice legit yachts afloat that will eventually turn up....cheers

Scott