2001 Grand Alaskan sea trial vibration issue..thoughts?

I realize I am a little late on this one, but despite me not being a mechanic I have chased vibrations on 2 boats. In my limited experience money given to the right professionals can solve the vibration issues provided the vibrations are a result of drivetrain issues. If the vibrations are coming from exhaust issues creating cavitation or some hull problems or some marlow velocity struts/keels then all bets are off. If the boat is in S Florida and it is determined to be a drivetrain issue I think you have a good chance of solving the problem. To my eyes that rudder is not slightly bent and it is highly likely that that bent rudder is not “lined up” or towed in properly with the other rudder. It makes you think that a hard grounding occurred and if that is so, is there movement in the struts as I would want to check the mounting of the struts and rudders. Next I would do is hire an outfit that does laser alignment. Pull the shafts and send out to check for straightness and start all over irregardless of what the owner said was done. You may have to spend money that you don’t need to unless they find a smoking gun. In others words, replace all engine mounts whether they are known to be a problem or not. I had an occislating shaft that was bothering me and sent videos to my service providers and was told it was misalignment and to keep running. Of course I was in the Bahamas. Fortunately I made the crossing back to florida and my transmission cracked its case. So was the shaft occislating the problem or was the shaft occislating because an internal transmission issue? Any way all of that lead to laser alignment which did result in moving one strut. Now I have a very smooth running boat. My boat is 54’ and the flybridge is 2 decks above the struts and I could never feel it at the helm. So your description of the problem makes it sound significant to say the least. On my previous boat the bore of one of the props was the issue. That of course was the last thing checked. Lastly I realize this is a boat for sale so that complicates things. See if they could give you another sea trial and if accessible put your hands on the strut mounting plates and see if the vibration is isolated to one side. But you might could deduct a significant amount from the purchase price and solve this issue for less (with the right people) but that is a risk. I hope I have helped.

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!

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

Run Forrest, run

Some of the visible stuff in that survey like the exhaust issues alone would have stopped me from even going to survey and wasting money.

these are not just scratches on the keel... they re heavy gouges. Wth did they hit??

i m no expert in analyzing oil analysis reports but too many red flags there as well.

and the performance is just awful. This is not even a fast trawler it s a trawler

some of the issues like performance (or lack of) and exhaust leaks point to build quality issues. Others are lack of maintenance and care. Who puts a boat on the market with an overheating generator and cracked leaky exhaust?

there are some things that only a survey will reveal but this is not the case here. I would recommend that you hire a experienced captain to preview the next boat you will put under contract and have him present for a pre survey sea trial. It will cost you a few hundred bucks but could save you thousands in survey costs

Not as a disagreement to any of the above about walking away or putting burden solely on Seller to remedy all major issues prior to further negotiations. But I thought I would mention the following for the benefit of others. I recently read about an oil analysis lab that had erroneous samples due to improper cleaning between samples. I cant find it after a short search. I am older but not demented. I know I read it as that same lab gave me to red flags for elevated copper on both engines. Also while I agree to take samples upon survey I think that one shot samples are subject to a lot of interpretation. I annually sample my oils and have had yellow readings that concerned me only to be told by mechanics to ignore it and keep running. I have been told that Man does not have any specs on iron, copper, etc for oil intervals. I think I am describing that correctly.