2002 5,7 Mercruiser exhaust manifold keeps cracking - 5 times this summer

[mart284]

Hello everyone!
I need help diagnosing the issue I have been fixing 4 times this summer, without much success sadly!
After doing proper maintenance last winter and taking the engine off for small oil leak fix, I have had a 5 exhaust manifold cracks on port side engine and port side manifold. Similar issue is described here: https://forums.iboats.com/threads/2003-mercruiser-6-2-mpi-exhaust-manifold-cracks.662180/ but without the concluison, what was the culprit for thsi!
History:
First time water in the engine and found a crack on manifold - deductive team decided that it is due to old age, replaced with same part.
Second time was 2 hours drive later - conclusion was that it is manufacturer issue and I got two bad parts, replaced with different manufacturer part.
Third time it failed after few hours of driving and this time hydrolocked the engine. Took the engine off, to bits and pieces, replaced bent rods, found wrong gasket between engine and head with signs of leaks and assumed this was the reason..
Fourth time, after few hours of driving, water is back in the same place. I am utterly pissed and did not take it apart yet, but symptoms match with for previous cases.

My ideas so far - issue is related to lack of cooling water in third cylinder manifold, but I can not find the reason for it. Any hints or tips are awaited..

Boat is 2002 Sea Ray Sundancer with 5,7 MPI and Vdrives.

 

[Scott Danforth]

sporadic cooling water.

manifold runs without water, gets to 900-1100 degrees, gets a slug of cold cooling water..... instant cracked casting

you also burned up all the rubber bits in your exhaust as they are only rated to 250 degrees

start at the inlet strainers and go thru every inch of your cooling water system all the way thru the exhaust. you will need to remove, inspect, etc. you will find the issue on your cooling water.

 

[alldodge]

What is your serial number and are you open or closed cool?

 

[mart284]

Hi
I have sea water cooling and I do not know the serial number of the engine. While driving all numbers are fine on numbers, water pressure, water temp, oil pressure etc. Water coming out from the sides of the boats are normal temp, if the manifold would get really hot, it should burn the paint as well? All 4 of my used manifolds are looking like 2 hour old
image1
image

 

[alldodge]

IS your cooling system like this one, or is it different?

 

[cyclops222]

Someone removed the TALL exhaust manifold heat risers. And or the boat is stopped very fast from a planning speed. The cold water runs up the exhaust system and into the cylinders. VERY COMMON problem in engines With modern cams having OVERLAPPED timing of the INTAKE and EXHAUST valves both open at the same time. My expert mechanic 1 time failed to add the taller exhaust risers when he installed a brand new engine............. It does happen on old engines being updated.

 

[mart284]

My setup looks very similar to the drawing attached - will go over it pipe by pipe once in the boat. Thanks!

Cyclops - Searay has rather big mufflers and it is not the issue with fast stopping, I am sure I have the issue with water flow around this one exhaust manifold - it started after the engine removal for the maintenance last winter. Just need to figure out, what is now different from last seasons...cracked manifold and engine bay

 

[cyclops222]

They forgot to install YOUR ORIGINAL exhaust risers.
Or put someone elses short risers on.
Only so many ways to crack Cast Iron Risers and Exhaust manifolds.
By now warped / leaking cylinder heads are a real possibility.
only other possibility
Is the engine oil on the dipstick a light brown color due to water in it ?
Rare possibility. Intake valves on 1 side sticking open ?
The water to reach the manifold from the back of the boat ?
Does anyone else drive the boat ?
Do you very quickly pull the throttle to idle when stopping ?
I feel they do not have a correct riser on that on side. If the riser is TOO short ? Water Hydro locking is REAL at normal driving. I helped remove sparkplugs from a hydrolocked engine 3 times on 1 cruise. Replacement engine did not have correct Risers.

 

[alldodge]

I looking for just how the water flows thru the motor and out to see if there is something on the port side which can restrict flow. The port side is always a slight bit hotter on most just because that's the way the motors are built

As Scott mentioned it can also be the mufflers. If the port side has collapsed some then the temp sensor in the thermostat will show motor is running at correct temp, but the port side manifold can be getting very hot

 

[cyclops222]

They did not install YOUR engine !! ? SOMEONE elses engine.

 

[mart284]

They did not install YOUR engine !! ? SOMEONE elses engine.

Winter maintenance was done in the boat and last renovations I was the delivery guy to and from the garage - engine is mine

 

[mart284]

I looking for just how the water flows thru the motor and out to see if there is something on the port side which can restrict flow. The port side is always a slight bit hotter on most just because that's the way the motors are built

As Scott mentioned it can also be the mufflers. If the port side has collapsed some then the temp sensor in the thermostat will show motor is running at correct temp, but the port side manifold can be getting very hot

We assume that it is linked to the water flow thru the exhaust, just can not find the issue, last time engine and all the piping was outside the boat and we did not see any issues (to be frank - we also did not look any closer on piping) SeaRay mufflers are rather big bulky ones and there is water flow out of both engines - water is not burning hot and temp seems to be similar on both engines - checked by "toe termometer" I will ask to check the port side flow once more - thanks!

 

[mart284]

They forgot to install YOUR ORIGINAL exhaust risers.
Or put someone elses short risers on.
Only so many ways to crack Cast Iron Risers and Exhaust manifolds.
By now warped / leaking cylinder heads are a real possibility.
only other possibility
Is the engine oil on the dipstick a light brown color due to water in it ?
Rare possibility. Intake valves on 1 side sticking open ?
The water to reach the manifold from the back of the boat ?
Does anyone else drive the boat ?
Do you very quickly pull the throttle to idle when stopping ?
I feel they do not have a correct riser on that on side. If the riser is TOO short ? Water Hydro locking is REAL at normal driving. I helped remove sparkplugs from a hydrolocked engine 3 times on 1 cruise. Replacement engine did not have correct Risers.

Risers and elbows are not original, when I got the boat, all risers and elbows were changed to new better ones. Cylinder heads went to the shop and were checked and refurbished - no issues there.
Engine oil this 5th time is still clear as engine was stopped before it was filled with water, all previous times oil was creamy-coffee e.g mixed with water.
I am the only driver and Sundancer 320 muffler system is built in a way that it is almost impossible to hydrolock the engines.
I have manifold, extra risers and elbows checked after 4th crack, everything was fine except the crack in the manifold - always in similar spot hence the idea that cooling water is not reaching to certain spots during the drive...

 

[mart284]

I looking for just how the water flows thru the motor and out to see if there is something on the port side which can restrict flow. The port side is always a slight bit hotter on most just because that's the way the motors are built

As Scott mentioned it can also be the mufflers. If the port side has collapsed some then the temp sensor in the thermostat will show motor is running at correct temp, but the port side manifold can be getting very hot

My boat mufflers and exhaust outlets are looking like this, so sudden stopping is not bringing wave to the engine. I will be checking the whole waterflow in and out on that side of the engine - can also compare to starboard side, if there is any differencies.

 

[mart284]

I would exclude the muffler part - during the run and different check, elbow is always cold, meaning that muffler is not restricting it, still seems to be linked with water flow thru the manifold himself

 

[mart284]

One more question - I have dry joint risers and need to verify where to put seal with the small hose? I watched several videos and it stated that it should be below hose coming in? Anyone has a good drawing on how install those, please?

 

[cyclops222]

You live in a area with ZERO good marine mechanics.
Are you still using the same brand of parts ? Same repair place ?

 

[alldodge]

One more question - I have dry joint risers and need to verify where to put seal with the small hose? I watched several videos and it stated that it should be below hose coming in? Anyone has a good drawing on how install those, please?

Yes, the hose coming in is where the restrictor hole goes

 

[mart284]

You live in a area with ZERO good marine mechanics.
Are you still using the same brand of parts ? Same repair place ?

Hi

I live in Estonia, Northern Europe, it is a small country just a bit south from the place where Santa Claus lives Hence we do not have much US origin boats here and Mercury is not the most popular brand on engine. I do hope that my mechanic is the best one in the country, but having a crack on manifold 5th time requires some help from outside. Changed the manifold brand twice without a difference...

 

[mart284]

Yes, the hose coming in is where the restrictor hole goes

I have the hose coming to the riser, should the restrictor be lower or higher from the hose?