Cracked block???? 4.3 mercruiser

woodlaker · May 18, 2009

I have a 2001 Glastron with a 4.3 Mercruiser engine. The engine did not get drained and winterized properly last fall. I found a soft plug that was popped out of the left side of the motor. I replaced the plug, hooked the water muff up to the outdrive and started the engine and let it run for 5-10 minutes at different RPM's. It ran fine, good and smooth, got it warmed up and shut it off. I pulled the dipstick, but the oil looked good and at the correct level. When I drained the oil, it was milky like there was water getting into the oil. It also smelled gassy. Do I have a cracked block? Does the motor run that good if it is a craced block? Could something else be cracked? If anyone has had any experience or problem with this, any advice would be appreciated. Thanks

IVAZ · May 18, 2009

Re: Cracked block???? 4.3 mercruiser

Welcome to iboats.
Cracked blocks from freezing dont happen much in my area, so youre going to need other people to chime in and give you better advice.
From what I read here (which lately its been a common subject) you might have only/also cracked heads. Many of these guys are also claiming that it ran good and cant believe it is cracked.
A common thing to do is to get an expandable rubber plug to temporarly block the hole and run it for a little bit to see if you still get the water mixture.
Sorry for the bad news but you most likely have a cracked block.

danond · May 18, 2009

Re: Cracked block???? 4.3 mercruiser

Run a compression test on all the cylinders and see what you get. That's usually a good place to start.

Not sure why it smells like fuel...

A popped casting plug is a bad sign, though.

gshldon · May 18, 2009

Re: Cracked block???? 4.3 mercruiser

if you have a gassy smell in the oil it is not a good sign, it could be a bad head gasket or maybe a bad ring, checking the compression would be a good place to start to see if you have a cyclinder that is low on compression. If all is good on the compression test, change the oil and run it again and drain the oil and see if you still have a gassy smell and if you do then i would check the head gasket.

Good luck

woodlaker · May 18, 2009

Re: Cracked block???? 4.3 mercruiser

IVAZ said:
Welcome to iboats.
Cracked blocks from freezing dont happen much in my area, so youre going to need other people to chime in and give you better advice.
From what I read here (which lately its been a common subject) you might have only/also cracked heads. Many of these guys are also claiming that it ran good and cant believe it is cracked.
A common thing to do is to get an expandable rubber plug to temporarly block the hole and run it for a little bit to see if you still get the water mixture.
Sorry for the bad news but you most likely have a cracked block.

Thanks IVAZ. I am confused, not sure what you mean by expandable rubber plug to temporary block the hole, what hole are you talking about?
Thanks for the info.

woodlaker · May 18, 2009

Re: Cracked block???? 4.3 mercruiser

danond said:
Run a compression test on all the cylinders and see what you get. That's usually a good place to start.

Not sure why it smells like fuel...

A popped casting plug is a bad sign, though.

Thanks, I will try that. I see you are from Bismarck, I live in Devils Lake. Sounds like you will have plenty of water in the Missouri this year as we do in the big lake.

woodlaker · May 18, 2009

Re: Cracked block???? 4.3 mercruiser

gshldon said:
if you have a gassy smell in the oil it is not a good sign, it could be a bad head gasket or maybe a bad ring, checking the compression would be a good place to start to see if you have a cyclinder that is low on compression. If all is good on the compression test, change the oil and run it again and drain the oil and see if you still have a gassy smell and if you do then i would check the head gasket.

Good luck

Thanks for the additional information. I suppose the only way to tell if it is a head or head gasket is to tear it down.

IVAZ · May 19, 2009

Re: Cracked block???? 4.3 mercruiser

I re-read your post. I missed the part where you stated you put the plug back in (it is a core plug you are talking about right?). Sorry fo the confusion.

180shabah · May 19, 2009

Re: Cracked block???? 4.3 mercruiser

Pressure test the cooling system - that will tell your if the block is cracked or not. That just leaves the manifolds, but when they leak the water will be IN the cylinders not under them.

danond · May 19, 2009

Re: Cracked block???? 4.3 mercruiser

woodlaker said:
Thanks, I will try that. I see you are from Bismarck, I live in Devils Lake. Sounds like you will have plenty of water in the Missouri this year as we do in the big lake.

Definitely. I will be looking out for all the new logs, stumps and other debris this year!

Good luck with your engine. Luckily the 4.3 isn't hard to find or replace.

searay3 · May 19, 2009

Re: Cracked block???? 4.3 mercruiser

If you have gas and water in the oil and it wasn't properly winterized, etc. Start looking at a long or short block. You can investigate further if you wish, but there is no saving that block. Manifolds are probably toast as well. You'll have to pressure test those individually as the cracks may be internal. All the other marine stuff is probably ok, alternator, starter,etc. Personally, I would go with a long block. Heads are questionable as well.

woodlaker · May 19, 2009

Re: Cracked block???? 4.3 mercruiser

danond said:
Definitely. I will be looking out for all the new logs, stumps and other debris this year!

Good luck with your engine. Luckily the 4.3 isn't hard to find or replace.

Do you know of anywhere in ND to get a marine 4.3 or any parts or just even a reman.

180shabah · May 19, 2009

Re: Cracked block???? 4.3 mercruiser

Check out Rapid-O marine in Florida - even with shipping they are usually competitive. Or contact a local engine builder, find out what they would charge to build you one. Just don't let them go crazy with all of the usual "speed" parts.

woodlaker · May 19, 2009

Re: Cracked block???? 4.3 mercruiser

Thanks guys for the info. Who can pressure test the heads, or cooling system or the exhaust manifolds? Can any marine shop or does it have to be a machine shop. Not sure of the procedure.

180shabah · May 20, 2009

Re: Cracked block???? 4.3 mercruiser

Cooling system can be pressur tested right in the boat by anybody with a compressor(low pressure <10psi). You've basically got three "holes", the hose from the drive to the circulating pump, and the two hoses to the manifolds (one per manifold). Block off two of them and hook the compressor to the third. Either it will hold pressure(good) or you will hear the leak(bad).

woodlaker · May 20, 2009

Re: Cracked block???? 4.3 mercruiser

180shabah said:
Cooling system can be pressur tested right in the boat by anybody with a compressor(low pressure <10psi). You've basically got three "holes", the hose from the drive to the circulating pump, and the two hoses to the manifolds (one per manifold). Block off two of them and hook the compressor to the third. Either it will hold pressure(good) or you will hear the leak(bad).

Even if it is cracked internally will I be able to hear it leak?

180shabah · May 21, 2009

Re: Cracked block???? 4.3 mercruiser

Yes, and the pressure gauge will drop.

woodlaker · May 22, 2009

Re: Cracked block???? 4.3 mercruiser

Thanks guys, I will try those suggestions.

1980Galaxy · May 23, 2009

Re: Cracked block???? 4.3 mercruiser

Bubba1235 said:
I would not waste the time and money trying to determine if there is a crack in the block, there is. (The fact it had milky looking oil is the confirmation.) Ok, there may be the rare one in a million chance but in all my years of working on marine engines I have never seen a case where the block froze hard enough to pop the freeze plugs and didn't crack the block. I am certain enough I'd bet a months wages on it. Sorry...

Not to be mean but I see so many boaters wasting time, money and effort in the hope that they got off easy and it just doesn't happen.

i agree... i have the same situation with the same symtoms and (believe it or not), cracked block. i gave up on trying to fix or save it. just gonna hafta look around for a new block or engine.

Jet Lag 176flyer · May 23, 2009

Re: Cracked block???? 4.3 mercruiser

bud sorry to say that your block is probly cracked. i had the same thing happend same freeze plug pushed out etc.... the block was toast altho the rest of the engine was fine IE heads manifolds etc. repowered with new engine damn that hurt 7600.00 later and i learned a valuable lesson.

Cracked block???? 4.3 mercruiser

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