Re: Westerbeke 4-107 repair or replace?
It's not a common engine here in the UK, so I don't know much about the unit.
Run it in the boat a while and get a good opinion as to what is wrong with it. Put a compression meter on each of the pistons. Listen to the bottom end. Put an oil presure guage on there too, if you can. If the crank is scored, I would look at a recon motor as just about everything else is likely to be worn. The figure of 4k$ will buy a lot of recon motor.
With a couple of friends, and like 1/2 hour with a light-duty crane, you can lift out the motor.
Place it on a palate and take it home.
Strip it and find out what is wrong. Excessive mechanical noise normally leads the owner, and quickly, to the problem.
If you are going to replace the motor, put the same design of motor and gearbox in there again. You really do not want to get in to the problems of different engine mounts. They can be quite a headache.