Offshoreonly.com - Water in #6 and a small shake

Water in #6 !!! Here is what happened:

When I started up cold Saturday morn, the motor must have had a tiny bit of water in cyl because it hesitated once in the crank cycle. I thought the battery was low as that is what it sounded like while cranking. But it started fine.
I then drove 15 miles and put gas in boat. Motor started 100% fine after fueling up. After a 45 mile run, I shut off and drop anchor. After about 10 minutes I started up again for a minute. Started fine, but I "kinda" thought it sound just ever so slightly "off". Like "maybe" there was a slight miss - maybe?!?!?

We partied for about 2-3 hours and I try to start my motor. Starts to crank (not start) then locks up. I find that only #6 is full of water. Remove plug and crank to remove water (Thought is to clear water and run home) good amount of water comes out. Wait a few minutes, and repeat - a little bit of water comes out. Wait a few more minutes, and repeat - a little bit of water comes out. Wait a few more minutes, and repeat - a little bit of water comes out. At first I thought headers were leaking. Did pressure test Sunday, headers are 100% fine. There is some water in oil. Noticed oil level was about 1 quart over full, still looked good on dip stick though. But on the bottom of the oil fill caps on valve covers - milkshake!

Not that it matters, but motors are run 99% of the time @ 3500 - 4000 RPM and maybe 10 minutes total time WOT. Motors have 100 hours on rebuild - they have not been run hard and have had better care than most people care for their kids.

So I limped back at 7 - 8 mph. Now THAT sucked!!

So I am thinking I have either a blown head gasket, cracked head or cracked block. Any ideas?

PS: Boat is now in NC in the care of Joey Griffin as he is the one that built the motors. I guess I'll hear what the problem is in a few days, but still curious to hear from all the motor wizards what the best guess is.