[Showtime]

Hello All,
I have a '93 Tiara Open located in Newport Beach, CA. I bought it three years ago. Paid $50k for it.  The boat was in great condition but with both 350 gas Crusader engines having 1600hrs. However, the previous owner kept all maintenance records and it was well maintained. I put about $20k into fixing areas that were old. Due to health issues, I decided to sell it but took "one more" trip to Catalina Island (26mi each way). You guessed it...half way back the port engine overheated. I quickly shut it off as I saw the temp gauge going up. I limped back to dock. There was coolant spray over the port engine that came from the overflow bottle.
After the engine cooled, I started the engine for a minute. Then when I went to start it again, there was a "clunk" and it wouldn't turn over.  I had two mechanics look at it. One checked the oil and said the oil level was high. He pumped out oil that also had coolant to maybe seawater in it. One said "new engine", the other was more optimistic saying possible head or engine rebuild. 
Does anyone have experience with a similar failure? If so, what was the finding? A cracked block was tossed out as was broken crank shaft? One said no way to know without pulling the engine from the boat.
Does anyone think the engine could be repaired without pulling the engine?
I appreciate any feedback you all have. 
Many thanks!

[Capt. Paul]

Sounds like water got in the oil perhaps through a bad oil cooler.
Pulling the heads should reveal if you have bent rods from hydro lock. If not, you should be able to reassemble with new gaskets and have the oil cooler and heat exchanger pressure tested to see how water got into the crankcase.

[hiccup]

Internet opinions from people who have never set eyes on the motor aren't worth much, but that sounds like a catastrophic failure to me. Overheat lead to something cracking (manifold?) or warping (head?) and coolant got where it shouldn't (cylinders?), and some metal broke or bent. Engine must come out, who knows if it can be rebuilt or you're looking at a new short block, long block, whole new engine. It's unfortunate but it is what it is.

[Capt. Paul]

Hello All,
I have a '93 Tiara Open located in Newport Beach, CA. I bought it three years ago. Paid $50k for it.  The boat was in great condition but with both 350 gas Crusader engines having 1600hrs. However, the previous owner kept all maintenance records and it was well maintained. I put about $20k into fixing areas that were old. Due to health issues, I decided to sell it but took "one more" trip to Catalina Island (26mi each way). You guessed it...half way back the port engine overheated. I quickly shut it off as I saw the temp gauge going up. I limped back to dock. There was coolant spray over the port engine that came from the overflow bottle.
After the engine cooled, I started the engine for a minute. Then when I went to start it again, there was a "clunk" and it wouldn't turn over.  I had two mechanics look at it. One checked the oil and said the oil level was high. He pumped out oil that also had coolant to maybe seawater in it. One said "new engine", the other was more optimistic saying possible head or engine rebuild. 
Does anyone have experience with a similar failure? If so, what was the finding? A cracked block was tossed out as was broken crank shaft? One said no way to know without pulling the engine from the boat.
Does anyone think the engine could be repaired without pulling the engine?
I appreciate any feedback you all have. 
Many thanks!

---

You have probably figured it out by now, but if it were mine, I would pull the spark plugs and see if it will turn over by hand.
A socket and breaker bar on the crank pulley will do it. If it turns, you can use a wood dowel in the spark plug hole and turn the crank pulley through a complete cycle to measure the stroke or see if one hole is deeper at the top of the stroke.
Sounds like you got coolant or sea water in the oil. It is possible that MAYBE you didn't bend a rod. If all seems well, find your issue (oil cooler maybe), repair that and be on your way.
While likely, it is not a given that a rod is bent.