Hey all, 

2003 Universal M35BC. 

At a pretty big decisional branch point with our engine and could use some wise input.   Very long message warning.  

When we purchased the boat we had an engine inspection by a well-reviewed mechanic.  Despite the exterior of the engine showing signs of corrosion the mechanic's inspection was "runs great- clean 'er up and she'll last forever".  The oil analysis was near perfect without any evidence of abnormal amounts of metal etc.  Engine runs really well and very smooth.  

I've cleaned up a lot of the external corrosion and it was clear that there must have been a chronic coolant leak from a leaking cap, with corrosion evident on the manifold and wherever gravity led the leaking coolant.  

I'm replaced my coolant lines yesterday and couldn't believe how corroded the exhaust manifold fitting was for the hose between the manifold and heat exchange.  See pic.  It has lost a chunk from the bottom and looks like it could crumble any day.  I cleaned it up the best I could and was able to get a new hose on and tighten the hoseclamp as per normal.  The other fittings for the other hoses looked ok.  I ran the engine for a few hours and temp remained at 165F with zero leaks.  

So, my first issue/question is:  clearly I need a new manifold.  I think this'll probably last me through the season but I can't see this lasting more than a year.  Who knows, but not a risk I want to take.  I did a quick search and looks like new manifold will run me around $2300.. ouch.  I'd outsource that job (though if someone here has done it and it's not brutal I could do myself).  but figure around $3K with labor if I hire someone.  

My other question:  while running it yesterday at temp, I was in the aft cabin watching for leaks.  And, I noticed an almost imperceptible vapor/fog/steam/smoke (?) coming from the breather hose that comes from top of crankcase.  First off, the hose is sitting right next to the air intake and I'm guessing that's not ideal as it's just recirculating whatever is coming from hose.  I'd say there's a very faint exhaust smell, but no more than usual for a diesel.  CO detector in that cabin hasn't alarmed, for what it's worth, though I understand there's not as much CO in diesel exhaust compared with gas. 

I had changed my oil in May, and it remains dark without any frothing/evidence of water/coolant.  

No low oil pressure alarms, and again engine temp is fine.  

Dilemna/concerns: 
1) what's the story with this steam/vapor that I'm seeing from breather?  some sources online said it's normal, others say the world will end.  Anyone have some knowledge on this? 
2)  $3K is a big chunk to put into an engine that already shows significant corrosion.  Though I'd love to think that it's isolated to the manifold, this is probably a pipe dream and I worry that once the old manifold is off we'd see lots of corrosion elsewhere and then the question is whether it's worth it to even put the new manifold on.   
3)  looks like repowering with a Beta 30 would run me around $13K for the engine alone, plus potentially an equal amount in labor.  Huge chunk.   

We plan to keep and regularly use the boat over the next ten years at least.  So I'm really struggling with which way to go here. 

I think if the breather vapor is a sign of deeper badness, like head gasket failure etc, the decision is made.  Repower.  But with the engine running so smoothly I just can't imagine there's something already catastrophically wrong.  

Of course, one option that I'm sure many would choose would be to just keep running the engine as is.  Hose is on, not leaking, and maybe it's possible that now that the boat is owned by someone doing vigilant maintenance with coolant flushes etc the corrosion progression will be slowed.  And, just run it until it dies.  And then repower.  The downside being that it would suck to repower in the last two years of owning the boat, which as luck would dictate, would be the case.  

The other issue is the difficulty sourcing parts for this engine.  Now that Bayshore in Annapolis has closed, it seems limited to a few online sources with finite stock.  Not ideal.  

I realize there are no "answers" here.  Just looking for some input, and if anyone has repowered with the Beta I'd love to hear about the experience.  

Thanks all, and sorry for the crazy-long message.  

Brad