Mercruiser 4.3 V6 rebuild fail.....so next step?

[dpb]

Yesterday was first start of the engine after a full rebuild, started and ran fine. After running for a few minutes stopped it to check things over.
Found that the oil is now mayonnaise so clearly water getting to it.
It is a part of a project boat which serves mainly to keep me busy during retirement so no panic other than I know I need to do something sooner than later to avoid internal damage.
The reason for posting is to pause and see if there are any points that I should be considering before diving in.
How I got to this point:
I acquired the engine with seized pistons and valve and head damage. It came with manifold and risers off and new ones supplied, all looking like corrosion in bores and valves caused by exhaust component failure.
The engine was taken apart and was rebuilt with the following:
Crank reground with appropiate new bearings used.
New pistons, rings fitted.
Block rebored for new pistons. (carried out by engineering company)
Reconditioned heads complete with new valves etc fitted. (Bought from specialist)

I realise now that somewhat stupidly I did not check the block specifically for cracks but then I did not discover anything during the dismantle to point in that direction, in particular no emmulsified oil residue anywhere.
Anyway, I have removed the emulsified oil as much as I can for now, the level on the dipstick had gone up by 30 to 50mm.
Also the water has been drained. During that process I noticed that very little water came out of the right bank, which I drained first, but plenty out of the other bank. Poking around the drain hole with no flow did not seem to show a blockage. Is the water jacket on either side of the block separate? I thought it was all one joined up chamber.

So now I am thinking that the cause could be:
Cracked block. maybe at the bottom of the side of the block that did not drain.
Cracked cylinder head ie faulty from purchase
Cracked inlet manifold
Bad gasket joints, at cylinder head or inlet manifold
I am currently discounting exhaust failure as it was all new and I dont think the symptoms fit this cause.
Most of the rebuild was done 2 years ago so the engine has been sat in the garage for a while.
The engine has been sat in the boat over winter with tarp over it so rainwater could have got to it but surely the only way in is via the carb and that was sealed

My current plan is to remove inlet manifold and heads to see whats what and to allow oil to be poured over essential parts.
Wondering if worth doing compression tests, or turning the engine on the starter with fresh oil before dismantling.
May only do mimimal work now and address the situation next winter as we are away most of the summer.
I could fill the block after manifold and head removal with cheapo oil or even diesel to preserve the parts over the summer.

Any thoughts?... What have I missed?

 

[dpb]

I have decided to put new oil and filter on to run the engine without cooling for a minute or so to flush emulsified oil out, maybe change both and do again.
Should take the urgency out of dealing with it while I ponder.

 

[julians]

Yesterday was first start of the engine after a full rebuild, started and ran fine. After running for a few minutes stopped it to check things over.
Found that the oil is now mayonnaise so clearly water getting to it.
It is a part of a project boat which serves mainly to keep me busy during retirement so no panic other than I know I need to do something sooner than later to avoid internal damage.
The reason for posting is to pause and see if there are any points that I should be considering before diving in.
How I got to this point:
I acquired the engine with seized pistons and valve and head damage. It came with manifold and risers off and new ones supplied, all looking like corrosion in bores and valves caused by exhaust component failure.
The engine was taken apart and was rebuilt with the following:
Crank reground with appropiate new bearings used.
New pistons, rings fitted.
Block rebored for new pistons. (carried out by engineering company)
Reconditioned heads complete with new valves etc fitted. (Bought from specialist)

I realise now that somewhat stupidly I did not check the block specifically for cracks but then I did not discover anything during the dismantle to point in that direction, in particular no emmulsified oil residue anywhere.
Anyway, I have removed the emulsified oil as much as I can for now, the level on the dipstick had gone up by 30 to 50mm.
Also the water has been drained. During that process I noticed that very little water came out of the right bank, which I drained first, but plenty out of the other bank. Poking around the drain hole with no flow did not seem to show a blockage. Is the water jacket on either side of the block separate? I thought it was all one joined up chamber.

So now I am thinking that the cause could be:
Cracked block. maybe at the bottom of the side of the block that did not drain.
Cracked cylinder head ie faulty from purchase
Cracked inlet manifold
Bad gasket joints, at cylinder head or inlet manifold
I am currently discounting exhaust failure as it was all new and I dont think the symptoms fit this cause.
Most of the rebuild was done 2 years ago so the engine has been sat in the garage for a while.
The engine has been sat in the boat over winter with tarp over it so rainwater could have got to it but surely the only way in is via the carb and that was sealed

My current plan is to remove inlet manifold and heads to see whats what and to allow oil to be poured over essential parts.
Wondering if worth doing compression tests, or turning the engine on the starter with fresh oil before dismantling.
May only do mimimal work now and address the situation next winter as we are away most of the summer.
I could fill the block after manifold and head removal with cheapo oil or even diesel to preserve the parts over the summer.

Any thoughts?... What have I missed?

I think you're right about it being unlikely to be an issue with the exhaust manifold/risers, as if these were broken these would leak water into the cylinders and not into the oil.

A rise in oil level of 30-50mm from just a few minutes running is a lot of water. I guess the most likely cause is a cracked block as this is the only part carried over from the "old" engine, but it could be any of the things you have listed.

I guess if you just want to get it into a stable state where you can leave it over the summer, you could drain the emulsified oil out, refill, then just turn it over on teh starter motor with the spark plugs removed (so it doesnt fire) for a minute - might need a couple of batteries - to circulate the oil round the system and remove as much water as possible, then drain and refill with fresh oil and leave until you're ready to work on it. Might be less risky than running with no cooling at all.

 

[Aardee]

Start with the simple stuff. Are the heads torques down correctly and are the head gaskets seated well?

 

[vas]

and get rid of the seawater for 1-2 min tests, remove the whole seawater cooling

 

[dpb]

The boat is on trailer. No leg fitted.
Hose connected to coolant inlet on Bell housing. Tap opened just enough for adequate flow. Set up tested without engine running a week before engine test.
Also for engine test, water on before engine start.
The configuration of the elbows seemed to me to be such that water would rise up the elbow and be ejected to the exhaust down hill from the top of the elbow so as to run down and out the exhaust outlet at the transom..... which it appeared to do.
Am I right or was this a mistake?

 

[vas]

dont know the engines, but generally when on the hard with hose connected, its always engine starts first and THEN you turn on the tap...
someone that knows how these are wired/plumbed would be of more help than me.
you CAN run the engine for a couple of mins without any water going through. The only thing suffering would be the impeller.

 

[dpb]

No impeller as it is in the outdrive leg which is not present. Anyway two oil changes with a couple of minutes run after each change has left me with clear enough oil so time no longer of the essence. I want to try pressure testing the cooling system before diving in. Just figuring out how!

 

[spannerman]

The block is not divided so should fill equally from the water pump. Is the engine raw water cooled?, as the water passages between the block and head can get eaten away by rust which means the hole is too big and the copper ring in the head gasket which should crush and seal between head and block has nothing to clamp on it.
The other place it can leak is the water passage from the head to the inlet manifold, as stated the manifolds and risers are new so should be no problems there. Yes the water fills up the riser until it falls over into the exhaust.
If all these are ok then it points to a crack somewhere.

 

[Freebee]

you could do a compression test, what have you got to lose??

 

[dpb]

Thanks for all the helpfull comments.
The engine is raw water cooled.
I will do compression tests also.
I have just been looking at the photos I tool during strip down. No sign of emulsified oil anywhere. The oil filter was clearly not new and I would have noticed if that was full of emulsified oil.
My belief is that the last time the engine ran it was ok (5 to 10 years ago), though with failing exhaust components. Which led to water ingress to the pistons during storage and the piston and cylinder damage that was clear on dissassembly.
So either frost damage occurred during the storage period as the previous owner did not seem to know much about the mechanics so likely did not drain water jacket or I have not done the gaskets properly.
Any way. I will add to this when I get to the bottom of it!

 

[Anthony]

As someone who has also just rebuilt two of these and only had a chance to run them for a few seconds without water but the boat is scheduled to launch in 6 weeks, you are making me nervous!

 

[dpb]

Got back on this today before the rain returned!
My efforts at pressure testing the water jacket worked ok but didn't tell me much other than it definately was leaking.

So off with the inlet manifold.
Pictures attached.
The gaskets are still in place on the heads as rain stopped play but it seems to me that the problem may be a leak at the gasket between manifold and head adjacent to cylinder 5 as there is un mixed water in that part of the engine and signs of a possible water path on the head side of the gasket.
There dont seem to be any obvious cracks in the block or the inlet manifold so far.
I intend to remove the gaskets carefully to see if there are water marks behind them.
If I still think the problem is at the head / manifold interface I could then carefully fill the engine water jacket with water till it reaches the waterways in the heads and see if it stays there.
All comments welcome.