Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

[firemedicmonkey]

I am new to boats and I have been posting and getting lots of help from you guys on I just want to say thanks! Just to get up to speed the boat has been sitting for about 3 yrs w/o an unknown service history. It has a completed and proper history up till about 5 yrs ago and then who knows.

Here is what I got:
1992 Mercruiser 4.3 Alpha 1 with Thunderbolt IV
Engine Serial #: OD823128
Outdrive Serial #: OD760439

I was checking out the engine prior to test firing, I primed the oil motor with a drill and oil pump primer... I removed the block and exhaust manifold drains and... uh-oh I got water from the starboard block drain and nothing from the rest...

Then I noticed that both exhaust manifolds are cracked in about the same place in about the middle of the manifold. I will take pics tomorrow if the rain stops.

My question is now that that the winterization process is very questionable on this motor where do I start looking for more problems caused by improper or no winterization (i.e block cracks etc.) I don't want to order exhaust manifolds if I need a whole new engine... at that point it might be time to walk away from this boat!

 

[cooter2506]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

If both manifolds are cracked then I would assume that NO winterizaton was done. I would remove manifolds and look for block cracks. Remove intake manifold and look in the valley that is where(from what I understand) they crack internally. If boat is in good conditioin it might be worth putting some time and money into it to get her back her back on the water.

 

[firemedicmonkey]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

I am assumming since it was only water that came out of the starboard block drain that it was not winterized at all... Considering the source that doesn't surprise me and is why I am taking my time to go over this boat from bow to stern, and port to starboard...

So I'm looking for cracks in the lifter valley? Near the cylinder walls? Any Particular location?

I was also told to look near the oil pan...

Any other ideas?

I think I have a line on a good motor and outdrive combo for cheap...

 

[Bt Doctur]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

Might try plugging the hoses that went to the manifolds/risers,remove the inlet hose from the transom and clamp a garden hose to it,remove the spark plugs, and dipstick, turn the water on and wait.You`ll know soon enough if theres a crack someplace

 

[clarkmcmp]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

My 4.3 block was cracked just above the dipstick hole. I hear this is a common place. Found out later there are internal cracks as well. I had heard what oil and water mixed looks like but I had to see it to believe it.

 

[firemedicmonkey]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

I did not notice any water in the oil when I started working on it... I primed the engine with an oil pump primer again no water in oil...

But I don't figure I would find any water in the oil since I don't think that engine has been ran since the damaged occurred...

I like the pressure up the water jackets idea that will show any water jacket leaks that aren't visible... Any idea how long to wait?

 

[Bt Doctur]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

If your hear/feel water going thru the hose ,you`ll know quick,if you turn the water on and dont hear/feel it running then you may have dodged the bullet

 

[firemedicmonkey]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

Gotcha
Sounds like a quick and dirty way to know if I am looking at a rebuild or not...

I have been doing some reading on pressure testing the cooling system with air and basically doing a leakdown test... I am thinking that is going to be the eventual route I go to be absolutely sure...

Since the manifolds are cracked what are the chances that the risers are damaged as well?

Is there an easy way to test... From what I am reading I am confussed... I do better with pictures...

 

[gshldon]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

If you are looking to test your manifolds look in the sticky section of the forum and in there it will tell you and show how to test for leaks in the manifold by using acetone to check for internal leaks. If you find the block to be ok and only the manifolds are cracked i would suggest in just getting new manifolds and not worry about the manifolds or risers, as that is the route i went. Good luck

 

[HT32BSX115]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

Since the manifolds are cracked what are the chances that the risers are damaged as well?

Not all that great..... The risers are for the most part self draining.


If they're rusty, you'd want new risers anyway. You can get exhaust kits that include the manifolds, risers, gaskets etc anyway.

Also, when you pressure test the block, you take the exhaust system "out of the picture" anyway. You can remove the raw water supply hose from the transom, and disconnect/plug the hoses going to each manifold.

You can then apply pressure to the block via the raw water supply hose. you can also connect a gage to one of the hoses that went to a manifold to measure the pressure.

You should be be able to safely pump it up to about 15 PSI.

If you use air, you'll be able to hear any leaks. If you use water you'll have to put a valve on the supply hose and close it when you get to the 15 psi test pressure. Then observe if the gage drops when the valve is closed.


If you have cracked manifolds, you probably have a cracked block.

 

[firemedicmonkey]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

I found a set of upgraded (supposedly) new exhaust manifolds for like $350 on ebay... from what looks like a reputable company they have a big marine parts website so if its just the manifolds no problem... If it's the block too... I have access to a another motor but I don't know what kind of condition it's in either...

 

[slasmith1]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

if I go through the trouble of replacing the manifolds I always replace the risers at the same time as they are just as old and worn. otherwise it is kind of like wiping half your butt. IMHO good luck

 

[Gary H NC]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

Check ebasicpower for the complete kit..manifolds,risers,gaskets and all new bolts..

 

[firemedicmonkey]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

I did check them... pretty expensive if I remember... The ones I am looking at if I can salvage the rest of the motor and the risers... They are from Doug Russell Marine:
http://cgi.ebay.com/ebaymotors/V6-E...8302865QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

Includes:
Exhaust Manifold
Exhaust Manifold Gasket
Exhaust Elbow/Riser Gasket
Water Drain Fitting

Price $170 shipped a side of $340 for both

 

[firemedicmonkey]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

I got the manifolds off today: I looked at the risers except for being rusty in the water jackets they look intact inside and out so I am going to assume they are good but I might try a acetone test on them. (It might help clean them up)

I did a compression test on all the cylinders and all cylinders were @ ~150 psi cold... I am going to try and rig up a water / air pressure testing devices tomorrow and test the block...
Any suggestions on how to plug the lines coming from the thermostat housing to the exhaust manifolds?
Any suggestions on how to adapt the water / air to go in through the large raw water inlet hose?

Below is pictures of what I found:

Port Installed:

Starboard Installed:

Port with Riser Removed:

Starboard with Riser Removed:

Port Removed:

Starboard Removed:

 

[Bt Doctur]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

just loop the manifold hose at the housing .instead of normal routing of housing to manifold ,make it housing to housing.
remove the inlet hose from the transom end and stick a garden hose in it and clamp it tight on the brass garden hose end.or remove it from the housing , obtain another short hose and clamp the garden hose there.

 

[firemedicmonkey]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

I hooked it up to water... and let it run for 15-20 mins... (after I forgot the block drains, its ok I flushed the water jacket until the water that came out of the block drains was clear) I did not hear any water going into the cylinders or the oil dipstick... I periodically checked the oil and it was clear and the level never changed... So I am thinking I am in the clear but I want to air pressure test to be sure, (I ordered new exhaust manifolds, so waiting on them to come in!)

I had found a nice right up on here about how to go about the block pressure test, but I lost it before I could get i nice tutorial written up. Does anyone have that info or know where its at... I think it was Don S or one of the other Gurus

Any tips or ideas about flushing the cooling system once its back together? (it is aweful rusty in there!)

 

[firemedicmonkey]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

Is anyone out there?

 

[acke61]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

i'm having sort of a similar situation...i have water in my cylinders after an overheat and stall with the same engine as you...maybe we can help each other out....i'm kind of clueless as you...

 

[Paul eagen]

Re: Mercruiser 4.3L Cracked Exhaust Manifolds, what else could be broken?

i'm having sort of a similar situation...i have water in my cylinders after an overheat and stall with the same engine as you...maybe we can help each other out....i'm kind of clueless as you...

Jeremy, sounds like you have a blown head gasket. If it over heated the heads might have cracked also.