Cracked Block Q's

1

1997StingRay190

Seaman
Joined
Jan 1, 2009
Messages
57
Situation. The boat was sitting this winter in New Jersey and the person who owned it previously didn't drain the water from the block. I got the boat back to NC and let it thaw out inside.

One casting plug was pushed out. I did a ghetto leak test by pressurizing the cooling system to 45 PSI, I couldn't hear any leak and after ~ 1 minute there was still tons of pressure.

I changed the oil and after I had all the old oil out I poured 1 extra quart of oil in the engine to flush stuff out and make sure I got all the old stuff out, then pumped out that quart.

Then I put a mobile one oil filter on and ran the boat for ~ 1 hour with the outdrive in a tub of water. I was confident the block was cracked, but now I'm not so sure.

On the oil fill cap there was lots of condensation and I emptied it several times, however after ~ 1 hour of running the oil still looked pretty clean.

1.Could that huge mobile 1 filter be catching most of the water if the block is cracked?
2. Could the block not be cracked and all that water on the oil fill cap is from condensation from sitting so long?
3. Is it possible that the crack is so small that I need to get the boat in the water running high RPM which would pressurize the cooling system with lots of water before it leaks into the oil?

I've been beating my head against the wall trying to figure this out. The person I bought it from said they would help if it was cracked, but they are 600 miles away and I think its best if I find out sooner than later. I'm willing to pay someone to help me get this figured out. Please help.

Thanks
Sean
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Cracked Block Q's

OK,

I'm not sure you have a problem.

Are you worried about the small amount of condensation on the cap?

If that's all you have you may not have any cracks at all.

Just popping out the "freeze" plugs doesn't always indicate a cracked block.

My 454 had 2 soft plugs popped out and I have no cracks.

If you pressurized the cooling system and it held pressure, then it's not leaking.

Run it around the lake at fairly high speed (so as to heat everything up good) and look for water. It wouldn't take but a few oz of water in the bottom of the pan to produce condensation on the cap.

Since the oil doesn't get all that hot it would take a while to evap all the water out.

Also, if you have a leaky riser gasket and it's allowing a small amount of water into an open exhaust valve you could get a little past the rings (if it sat long enough) that it would cause a little condensation to show up on the cap....

Regards,


Rick
 
1

1997StingRay190

Seaman
Joined
Jan 1, 2009
Messages
57
Re: Cracked Block Q's

Hey Rick, thanks for the input.

I actually had the exhaust manifolds off and the water that feeds them plumbed so I could just direct it outside the boat (because it has the original batwing style 1 piece manifolds that are 12 years old, have 450 hours of salt water on them).

Someone said that at 15 PSI if there was a crack I'd be able to hear it, and at 45 PSI I couldn't hear a thing. I guess I just need to man up, buy the new exhaust manifolds, and do a WOT ( oh darn :) :p ) run or two around the lake.

Worst case scenario (I think), the block is cracked and it may ruin everything inside, which if the block is cracked I'd be buying a full engine (minus the accessories) anyway- so I don't really have anything to lose right?

My guess is that most likely I'll be able to find a remanned engine w/internals much cheaper than a full blown marine engine with accessories and manifolds, or am I wrong here too?

Also, what is normal oil PSI for a 1997 Mercruiser 4.3 (mine ran right around 40 or a hair over)? Will the PSI increase or decrease if water continually contaminates it?

Thanks for the help,
Sean
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,088
Re: Cracked Block Q's

1.Could that huge mobile 1 filter be catching most of the water if the block is cracked?
2. Could the block not be cracked and all that water on the oil fill cap is from condensation from sitting so long?
3. Is it possible that the crack is so small that I need to get the boat in the water running high RPM which would pressurize the cooling system with lots of water before it leaks into the oil?
Click to expand...

Ayuh,...

1),.. No way in 'ell....
2),.. Yes,.. That's My Guess...
3),.. No,.. It's Cracked or it Ain't...

At 45psi,.. It's a Wonder you didn't Blow out the headgaskets....

Here's what I think happened,....
The motor saw a Soft Freeze,+ blew out the coreplug, allowing it to drain after it warmed up,...
Consequent freezes couldn't do any Damage, because the block drained out thru the popped coreplug....
That's really the Only way a coreplug Can save a block,...

If it were a quick Hard freeze,... The Block would be Junk....

I think you got Lucky.....;)
 
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