Unless you want to litigate, it seems likely you'll just have to suck it up...
Unless you want to
repower, which hardly seems likely at 700 hrs, it's best to learn about whatever shortcomings the engine model has or might have and do whatever PM needed to prevent problems before they happen.
Unfortunately, that can include things that are not generally seen as 'preventative maintenance'. On my Tamd41 it included replacing as many of the oring sealed connections as possible with threaded or soldered and hose clamped connections, replacing all the
electrical system; more reliable starter, Delco
alternator and homemade engine
wiring harness, and removing the inadequate and leak-prone built in
raw water strainer with a
bronze Perko unit. I am about to take off the various
aluminum upper engine covers and have them anodized in an effort to cut down on a pretty bad
corrosion problem (but the engine is old and has not been run as much lately as it should). I also remote-mounted the
oil filter and drilled and tapped the (stainless steel!)
oil pan for a standard NPT fitting for a
remote oil drain...
It might be prudent to look at the aftercooler now before it has a chance to spray seawater into the intake; we had problems with both internal
leaks around the aftercooler hsg/aftercooler/coverplate, repaired by welding the hsg and liberal use of silicone on the square oring gaskets sealing the three parts. The persistent external
leaks were fixed by taking pieces of the original oring sealed copper tubing, soldering them into the
bronze cover, and replacing the tubing with standard hose and clamps.
As for the turbo, at 700 hrs it shouldn't need replacing; the
exhaust volute may be available by itself, either new or used. Call one of the myriad of turbo services available and tell them your story and you might get lucky.
I used to get really good service and prices from a place called MJM, in
Alabama, but I found out the old guy I always dealt with (the owner) died a couple months ago. The business is still open though, 800-331-0616, and might be a good starting (and maybe ending) place...