1997 Mercruiser 5.7 EFI blown head gasket

[khe]

Here are some photos of the tops of the pistons. The leftmost picture is an overall shot of the 1-3-5-7 bank with #1 on the left side. The middle picture is a view of cylinders 1,3 &5 and the rightmost picture is a view of #5 on the left and #7 on the right.

The piston top of cylinder 5 has almost no carbon buildup which is odd. I wonder if I have an exhaust manifold leak that is slowly leaking water into cylinder #5. Would that have caused the "fire slotting" of the block?

At any rate, I am going to test the exhaust manifolds for leaks before installing the remanufactured engie as I do not want to go through this again.

While the engine is out I think it would be prudent to replace the coupler as if it goes, the engine would have to come out again to replace that. At 26 years old and 1750 hours, I think it is wise to replace the coupler.

 

[ScottinAZ]

Here are some photos of the tops of the pistons. The leftmost picture is an overall shot of the 1-3-5-7 bank with #1 on the left side. The middle picture is a view of cylinders 1,3 &5 and the rightmost picture is a view of #5 on the left and #7 on the right.

The piston top of cylinder 5 has almost no carbon buildup which is odd. I wonder if I have an exhaust manifold leak that is slowly leaking water into cylinder #5. Would that have caused the "fire slotting" of the block?

At any rate, I am going to test the exhaust manifolds for leaks before installing the remanufactured engie as I do not want to go through this again.

While the engine is out I think it would be prudent to replace the coupler as if it goes, the engine would have to come out again to replace that. At 26 years old and 1750 hours, I think it is wise to replace the coupler.

not uncommon for the piston to be "steam cleaned" when there is water in the cylinder. That is likely the root source of your failure. While we dont know yet where the water came in, it was certainly in #5. Had the other cylinder gotten enough water in it when running, it would be squeaky clean as well.

as for what to replace with the engine out, If it were mine, I would be replacing the items that the engine needs to come out for if they fail. If your coupler is 26 years old, and 1750 hours, I would probably replace it.... may not be needed, or it could go pear shaped the next run out.... its easy (and relatively cheap) to replace it now. Same goes for everything otherwise hidden behind the engine that is a PITA to replace while its in there. Take advantage of the engine out time......

 

[khe]

not uncommon for the piston to be "steam cleaned" when there is water in the cylinder. That is likely the root source of your failure. While we dont know yet where the water came in, it was certainly in #5. Had the other cylinder gotten enough water in it when running, it would be squeaky clean as well.

as for what to replace with the engine out, If it were mine, I would be replacing the items that the engine needs to come out for if they fail. If your coupler is 26 years old, and 1750 hours, I would probably replace it.... may not be needed, or it could go pear shaped the next run out.... its easy (and relatively cheap) to replace it now. Same goes for everything otherwise hidden behind the engine that is a PITA to replace while its in there. Take advantage of the engine out time......

I am definitely going to replace the coupler as I do not want to go through this experience again. I hope to test my manifolds today - install a piece of rubber in between the riser and the manifold, fill the them with water and connect shop air to the hose to see if they produce bubbles. My concern is there may be a crack that only leaks when the manifold is warm.

I don't know how water was getting into cylinder 5 unless it was due to the breeched head gasket or a leaking exhaust manifold.

 

[ScottinAZ]

I am definitely going to replace the coupler as I do not want to go through this experience again. I hope to test my manifolds today - install a piece of rubber in between the riser and the manifold, fill the them with water and connect shop air to the hose to see if they produce bubbles. My concern is there may be a crack that only leaks when the manifold is warm.

I don't know how water was getting into cylinder 5 unless it was due to the breeched head gasket or a leaking exhaust manifold.

check the heads real good. Chevys like to crack the heads around the exhaust valve, especially in the center two cylinders.

 

[khe]

check the heads real good. Chevys like to crack the heads around the exhaust valve, especially in the center two cylinders.

I'll take a look at the head in addition to testing the exhaust manifolds. My boat has been in freshwater all its years and has not been run in saltwater. Usually, engines run in saltwater have issues with the risers and manifolds.

 

[ScottinAZ]

I'll take a look at the head in addition to testing the exhaust manifolds. My boat has been in freshwater all its years and has not been run in saltwater. Usually, engines run in saltwater have issues with the risers and manifolds.

agreed, but with the age of the boat, I wouldnt rule it out freshwater either. Mine is older than yours, but still had the riser rot out that I had to replace. Not a lot of salt water here in AZ..... The Chevy head cracking issue is relatively common on automotive usages, so is an easy thing to check for here. An overheat or two in its lifetime is often enough to get them to act up. The shop you had set up to redo the heads should be magnafluxing them before they really start. Some of these hairline cracks are a bugger to see with the naked eye, but a little non-destructive testing brings them right out

 

[Scott06]

I am definitely going to replace the coupler as I do not want to go through this experience again. I hope to test my manifolds today - install a piece of rubber in between the riser and the manifold, fill the them with water and connect shop air to the hose to see if they produce bubbles. My concern is there may be a crack that only leaks when the manifold is warm.

I don't know how water was getting into cylinder 5 unless it was due to the breeched head gasket or a leaking exhaust manifold.

some people test the manifolds by filling with acetone for exactly that reason. It wicks into smaller cracks.

Might be worth looking at the disassembled head or having it magged. I didn't want any issues when I repowered so I bought a new Barr Exhaust manifold and riser set. Not trying to spend your money but you could also upgrade to the newer dry joint style as well. I think the OEM kit at Michigan Motorz is about $1k

Correction - I had this mixed up non dry joint/center riser OEM is $1k. They have Barr Dry joint for about $1400. I don't see the center riser Barr kit not sure if it is out of stock, but Barr is equal quality to OEM.

Genuine MerCruiser 5.0L & 5.7L Exhaust Manifold Package (1987-2001)

860246Q11 807988Q03

www.michiganmotorz.com

 

[khe]

agreed, but with the age of the boat, I wouldnt rule it out freshwater either. Mine is older than yours, but still had the riser rot out that I had to replace. Not a lot of salt water here in AZ..... The Chevy head cracking issue is relatively common on automotive usages, so is an easy thing to check for here. An overheat or two in its lifetime is often enough to get them to act up. The shop you had set up to redo the heads should be magnafluxing them before they really start. Some of these hairline cracks are a bugger to see with the naked eye, but a little non-destructive testing brings them right out

Since the head and the existing block are ruined due to the fire slotting in between cylinders 3 & 5, I am going to swap out the bad engine with a remanufactured engine. The existing block and heads are going to be returned for the core refund.

The exhaust manifolds do not have any rust on the exhaust side but I am going to make an adapter to connect shop air to the hose on the bottom side of the manifold and insert a piece of rubber between the riser and manifold. If they pass that test, I'll try the acetone method.

 

[khe]

The plot thickens... I purchased a remanufactured long block from Michigan Motorz and picked up the engine yesterday afternoon. I spoke to their master mechanic for quite some time discussing the failure. I wanted to make sure I found and corrected the issue that caused the problem so I wouldn't be repeating this repair any time soon. He said the number one cause of the failure I experienced was interchanging the plug wires for #3 & #5 (plug wire #3 connected to cylinder #5 and vice versa). There is no way that could happen at the spark plugs as the wires wouldn't be the correct length. I figured it could happen at the distributor though.

I traced every wire from the distributor to the cylinders and discovered that someone had the plug wires off by one position on the distributor cap.

Distributor position---Actual plug wire destination
1-------------------------------------8
8-------------------------------------4
4-------------------------------------3
3-------------------------------------6
6-------------------------------------5
5-------------------------------------7
7-------------------------------------2
2-------------------------------------1

When I look at the factory diagram, the timing was advanced by one plug wire position or 45° advanced! I'm not sure if the ECM could compensate that much but could this be the cause of the fire slotting?

I've owned this boat for eight years and have not touched the plug wire position at the distributor. I only replaced the spark plugs about 400 hours ago and just unplugged each wire from the plug, replaced the plug and reconnected the wire in the same position and moved on to the next plug.

The firing order cast on the intake manifold is 1-8-4-3-6-5-7-2 which corresponds to the actual firing order just off by one position on the distributor cap.

 

[khe]

I pulled the engine yesterday afternoon and am starting to transfer the components to the remanufactured engine. A short wire harness was laying in the bilge after the engine was removed. Pictures are attached. Can someone tell me where it is connects? The wire colors are red and brown.

 

[04fxdwgi25]

The plot thickens... I purchased a remanufactured long block from Michigan Motorz and picked up the engine yesterday afternoon. I spoke to their master mechanic for quite some time discussing the failure. I wanted to make sure I found and corrected the issue that caused the problem so I wouldn't be repeating this repair any time soon. He said the number one cause of the failure I experienced was interchanging the plug wires for #3 & #5 (plug wire #3 connected to cylinder #5 and vice versa). There is no way that could happen at the spark plugs as the wires wouldn't be the correct length. I figured it could happen at the distributor though.

I traced every wire from the distributor to the cylinders and discovered that someone had the plug wires off by one position on the distributor cap.

Distributor position---Actual plug wire destination
1-------------------------------------8
8-------------------------------------4
4-------------------------------------3
3-------------------------------------6
6-------------------------------------5
5-------------------------------------7
7-------------------------------------2
2-------------------------------------1

When I look at the factory diagram, the timing was advanced by one plug wire position or 45° advanced! I'm not sure if the ECM could compensate that much but could this be the cause of the fire slotting?

I've owned this boat for eight years and have not touched the plug wire position at the distributor. I only replaced the spark plugs about 400 hours ago and just unplugged each wire from the plug, replaced the plug and reconnected the wire in the same position and moved on to the next plug.

The firing order cast on the intake manifold is 1-8-4-3-6-5-7-2 which corresponds to the actual firing order just off by one position on the distributor cap.

Perhaps someone didn't verify the timing of the dizzy #1 wire tower with TDC on the crank when re-installing the dizzy. Then installed the plug wires and corrected it by twisting the dizzy till it fired it and timed it off that.

The pictures of where the #1 is all fine and good till someone does something, like pull dizzy out to replace an intake manifold. Who knows what has happened to it for over 25 years.

 

[Fun Times]

The wire harness in your photo's runs between the Distributor Module to Ignition Coil... Harness part number 84-817376T01... Very important part, take good care of it. $

817376T01 Distributor Module to Ignition Coil Harness - Mercury Marine | Crowley Marine

Find Distributor Module to Ignition Coil Harness - 817376T01 here. Offering discount prices on OEM Mercury Marine parts for over 50 years.

www.crowleymarine.com

 

[khe]

The wire harness in your photo's runs between the Distributor Module to Ignition Coil... Harness part number 84-817376T01... Very important part, take good care of it. $

817376T01 Distributor Module to Ignition Coil Harness - Mercury Marine | Crowley Marine

Find Distributor Module to Ignition Coil Harness - 817376T01 here. Offering discount prices on OEM Mercury Marine parts for over 50 years.

www.crowleymarine.com

Thank you for the identification! I would have eventually figured it out when I installed the distributor and ignition coil but it has been bugging me ever since I discovered it laying in the bilge.

$82.00 is highway robbery for that part! I'd bet you could get it from a GM dealer cheaper if it were still available or off a Cadillac Fleetwood, Buick Roadmaster or Chevrolet Caprice in the junkyard.

 

[Scott Danforth]

$82.00 is highway robbery for that part! I'd bet you could get it from a GM dealer cheaper if it were still available or off a Cadillac Fleetwood, Buick Roadmaster or Chevrolet Caprice in the junkyard.

It's a boat only harness.

 

[dubs283]

It's a boat only harness.

And I'm quite sure specifically designed for the est ignition system. I'm thinking the proprietary end that connects to the coil has a diode in it

 

[khe]

Perhaps someone didn't verify the timing of the dizzy #1 wire tower with TDC on the crank when re-installing the dizzy. Then installed the plug wires and corrected it by twisting the dizzy till it fired it and timed it off that.

The pictures of where the #1 is all fine and good till someone does something, like pull dizzy out to replace an intake manifold. Who knows what has happened to it for over 25 years.

When I install the distributor in the new engine, I am going to route the wires correctly so that it doesn't cause any confusion down the road. It is strange that someone would go through the trouble of re-routing the plug wires vs. correcting the distributor position.

 

[04fxdwgi25]

When I install the distributor in the new engine, I am going to route the wires correctly so that it doesn't cause any confusion down the road. It is strange that someone would go through the trouble of re-routing the plug wires vs. correcting the distributor position.

Trust me, have seen stranger thing done that just leaves me in absolute amazement.

 

[dubs283]

leaves me in absolute amazement.

You have no idea the amount of lazy, cobbled, incorrect and unsafe things I've seen on a boat

 

[khe]

The remanufactured engine is in the boat, the base timing has been set to 8° BTDC and seems to run fine. The engine vendor where I bought the engine told be to verify the total timing and I attempted to do that with it running on hose muffs. At 2400 RPM, the total timing was 38° advanced and the maximum spec. is 32° per the engine vendor.

While I was waiting for the tech. at the engine vendor to call me back, I called Mercury Marine's technical support line. The person I spoke with told me there was no mention of total timing in the shop manual, just the base timing spec. of 8°

I spoke to the engine vendor on Friday afternoon and they told me the ignition module has likely failed and is allowing the ECM to advance the timing too much. They said the module (same as an automotive application) is no longer available from GM and others are producing it. They said they've had good luck with the Sierra modules. I bought one and installed it and it made no difference in the total timing reading.

Since it was after 5:00 on Friday, I wondered if it needed to be checked under load so I took it out on the water and ran it around 2400 RPM and was seeing the same 38° reading so I backed it down and headed back to the ramp.

I am thinking the extra advance is what caused the issue and do not want to run the boat until I can get this sorted out. It's hard to believe that a new ignition module would be defective out of the box and usually when they are defective, the engine won't have spark.

The only other thing would be the ECM but the engine vendor said when they fail, it is always the driver circuit(s) for the TBI injectors so one or both injectors won't work and that's not the case here.

I am starting to wonder if I'm "chasing a ghost" and that the original failure was due to age/hours on the engine and not some failure of a component.