You really need to talk to a good diesel mechanic. If you're not going to use the turbo, you need to convert the engine back to a non-turbo setup IMHO.
I will agree with SD on this. Ask around local to you. I am cautious of things when I not know the facts behind why it not work. Now, if the boat is priced like the engine not work, I not have a problem buying, if, it what I want. I not pay for a 1/2 running engine.
I did put a Turbo Charger on my 1966 Mustang back in the 70's and it worked and I assume it would work without the Turbo or disconnected. But, if the Turbo is blown and junk like that, then I would check the oil and filter for debris.
Also, I never buy something I can not fix. That not mean I will not pay for labor, but, I want to know what going on, then I know if I pay someone, I know what I paying them to do, not what they tell me. I can tell some stories about this; real mechanic rips if I were not educated.
This may help get you started.
HowStuffWorks "How Turbochargers Work"