Water in engine - how likely is head or block crack?

Add me to the list of who's got a boat for sale... 1977Starcraft American fiberglass with 888 Mercruiser (Ford 302.) I recently inherited my dad's boat, pulled it out to get it ready for use. 2 of 3 freeze plugs (1st and 2nd) on the right side and 2nd on left side of the block were popped out. Right side head freeze plug popped out (front of engine) left side didn't (rear of engine.) My brother used the boat last season, didn't mention it to anyone, and didn't drain it. I replaced the freeze plugs, changed the oil, filter, fuel filter, and battery. Put a flush muff on the outdrive, turned the water on (first time I've used one) and started the engine. No problem. Idled smoothly, revved a little, sounded good, brought it up to about 2000 rpm smoothly, still sounds good. I see water dripping/running off the bottom of the exhaust manifolds. I can see freeze cracks on the bottom (each side) on the back end (under the riser) then I notice foamy milky oil flowing out the oil filler cap on the valve cover and out the dipstick. I throttled down and shut it off. Then shut off the water. I was bummed. I backed it into the garage for the day. Next day I drained the oil - about 1 gallon of water came out first, then milky thick emulsified water/oil. I put on a new filter, added new oil. I pulled the plugs. They looked damp as if by fuel. Smelled like old gas. No water droplets. I checked the compression (cold engine) and found 130, 130, 110, 160 on the left, 130, 130, 125, 130 on the right (is that about right?) I put the plugs back in and started it. No water (I know probably ruined the lift pump, but figured that's a minor fix compared to cracked block.) Engine started without problem and ran smoothly. I held it at about 1200rpm for about a minute. Does anyone have suggestions as to what I should do next? I am going to unhook and plug the octopus hoses to the manifolds and try to pressure test the water system with air (hopefully save having to change watered down oil again.) Does anyone think that my problem is anything other than an internally cracked block? I'm thinking that since I had "unmixed" water drain out first, that my garden hose pushed some in after I stopped the engine. Or could it have been pushed through the exhaust valve guides after going through a cracked exhaust manifold? What would be the best steps to take before buying new manifolds only to find out the block was cracked?
Thanks for any help or insight you can give me. I'm a newbie and all ears, learning more that I ever thought I could. sorry about the book i just wrote.

 

I don't think you would get water in the oil if it was a problem with the exhaust manifoil so I think the block is your problem.

If your lucky it's gaskets.

If yout unlucky start looking for a new block.

If you want to find out if it's not the manifoils just disconect the water on them

 

Buy a new short motor and manifolds --send your brother the bill.

 

Thanks for the quick replys, StianM and Frosty. I am going to start by tearing off the manifolds and heads in hopes that it is one of the heads or gaskets but will start looking for a new engine. I'll let you know what I find in the next week.

 

I just tore the heads off a 350 that was not properly winterized in so. Ky. and all I found wrong was two cylinders with standing water, a cracked exhaust manifold, and a leaking spier neck that let water sit on top of the manifold and leak past loose manifold gaskets into the motor. Water in the oil. Rebuilt the heads, replacee the exh. manifold, new gasketed with good sealer, flushed crankcase and oil galleries with cheap oil and a pint of atf, refilled with MC oil, and it fired up so fast it scared me. 100hrs later it will still push the 19' cobalt deep vee up to 55 by gps. I'd look deeper before I bought a motor. Maybe just a hefty water leak into the cylinders before you got it cranked from an internal manifold water leak thru open exhaust valves. Lots of standing water in manifolds.

 

Same scenario as yours but mine was the intake manifold. We first figured the head gaskets or cracked block..but when removing the intake to get to the heads we found the source of the water.

Best of Luck

 

Thanks guys, I appreciate your feedback. I was hoping to hear from someone who had similar experience and found it to be less of a problem than a cracked block.

I have decided to tear into it before buying a motor. I did find a used, matching motor (carb, manifolds, starter, alternator, etc) for $850. The boat shop that has it says they'd make the swap for $850 labor plus what ever gaskets I needed. Seems high? I think exhaust manifolds might cost less than a fourth of that. So I'm hopeful, and anxious to find out.

Thanks again. It may be a week or two but I'll post what I find.

 

I finally got to it. I thought I had water and sand sitting in the exhaust port of the last cylinder on the right side, but it was what drained down into the port when I took off the riser. It looks like the gasket (riser/manifold) was letting water in. Bolts were tight when I took it apart. see pictures uploaded. Should I look further? Intake manifold? I have found manifolds for $200 a side and a used engine for 850 + 850 labor to install ($1700 total.) Should I put it together with new gaskets and old manifolds to see if the water problem was gaskets? Any thoughts and suggestions would be appreciated. Thanks again.

 

Is your raw water lift pump mechanicaly driven by the engine? I was getting water in my sump on a diesel engine, the boat was afloat. When the head was stripped, water was found at the rear cylinder. My friend, who is a marine engineer, said that the water nearly always leaked at the rear cylinder.
After the engine was started again and shutdown, I deliberately left the inlet seacock open and after a few hours water had entered the sump again. I had already suspected the pump seals and so it turned out.
My pump was below the waterline and the water head did the rest when the engine was stopped. Using a hose could do the same and even build up sufficient pressure to overcome the oil pressure even when the engine is runnng. I admit to using a hose myself, I have a ball valve installed so that I can shut it on and off quickly, but the manuals normally ask that water is sucked from a bucket by the pump.

 

Thanks for reply murdomack. My pump is driven and it picks up on the sides of the outdrive. I think I'll have to look further. I can't really tell if water was sucked in through exhaust or not yet. I did look at the right side and found the same gasket markings and sand above the block off plate.

I think that the garden hose pressure may have been more than what the system would have had on its own. And you're right. I think the water should be sucked in by the pump.

I wish now that I would have taken it apart right after I shut it down when water got in the oil. I think that by changing the water/oil mix and running it a few seconds I may have dried and covered any "steamed" areas with exhaust gases.