1999 454 Mag MPI just quits - videos

Okay so Starboard is one of the old fireboat engines and I believe it is raw water cooled (no antifreeze).

I'm still stuck on that the rust on that head is relatively new and somewhat contained. The only event that corresponds to that is the replacement of the manifolds and risers before you made the trip. Sure it could be another undiscovered problem but I don't think so. It could be as simple as the riser bolts lost their torque during the trip which is common if you don't use a threadlocker or grade 8 lockwashers.

Regarding testing. In an ideal world, we bolt the riser onto the exhaust manifold with a gasket and rig up something to stop the air (plug) from leaking out the riser port entering the exhaust hose. Block off the raw water ports except for one connected to an air pump that will give you 15 psi. Dump the entire thing into a water trough (its heavy I know) and turn the pump on.

While it is possible you have a crack my money is on a bad seal at the riser gasket. It is a foolproof test since the riser and exhaust manifold are bolted together. However....I believe it will pass this test. Far more likely is the riser bolts lost torque and allowed water into the cylinders.

While you will not find it on the internet (except on CSR) I have learned my lesson regarding riser bolts and gaskets. Others might disagree which is okay but this is how I stop that problem from happening.

1) I use Red Permatex RTV High temperature sealant on both sides of the gasket to seal the gasket to the surfaces. I use the fiber gaskets not the graphite variety.

2) I use grade 8 bolts and grade 8 lock washers to bolt the riser on to the exhaust manifold

3) I used red thread locker on the riser bolts.

4) I torque the bolts in a cross pattern to 25 lbs.

I check the torque on them again after an hour of use. The reason why is because the bolts are long and will expand during a few heat cycles even with the lock washer and thread locker.

After a few cycles and checking the torque.....it stays constant.

Just my thoughts.....
 
Thx for the info. FWIW, the fire boat engines are closed cooling. I would NEVER have a raw water engine where I live except outboards, which are flushed after every use.
I always check for loose or not tight enough bolts when changing manifolds. I will move to red sealant and lock washers on the manifold bolts as a double precaution. I have come across loose bolts in the past.
I did torque to 30 lbs when I put them on. My bad, and maybe crushed a gasket. I usually get Sierra gaskets, and have used the green ones (fiber?) in the past.
 
370Dancer said:
Thx for the info. FWIW, the fire boat engines are closed cooling. I would NEVER have a raw water engine where I live except outboards, which are flushed after every use.
I always check for loose or not tight enough bolts when changing manifolds. I will move to red sealant and lock washers on the manifold bolts as a double precaution. I have come across loose bolts in the past.
I did torque to 30 lbs when I put them on. My bad, and maybe crushed a gasket. I usually get Sierra gaskets, and have used the green ones (fiber?) in the past.
Click to expand...
So you have block off gaskets between the riser and exhaust manifold? Did your original ones come with stainless steel block off plates?

A lot of people torque to 30. I just overkill on the lockwashers, rtv and thread lock because I have seen the exact problem you have caused by the bolts loosening and it fits the story. Plus when it does leak......it can be catastrophic.

On to the block off plates. Several iterations of dealing with Mercruiser riser leaks on closed cooling systems I ended up installing a solid stainless steel block off plate with a (green) gasket on top of it and below it.

I will be happy to give you the links to where you can get them. I freely admit I overkill on that riser to exhaust manifold joint because not making it water and pressure tight will cause it to fail.

While this did not happen in your case.....I have seen the fiber gaskets leak coolant because the fresh water side puts 15 lbs of hot coolant pressure against the gasket. Sure they will tell you it won't leak but I will tell you otherwise. Backing up the gasket with a piece of stainless steel guarantees it will not leak from either side.
 
Another thing I've done is that I've switched to a true high grade stainless fastener and converted it all to studs - sourced from McMaster. Now I can get much more consistent clamping force and don't run the risk of rust forming and causing an issue with removal.
 
By block off plate, I assume you must be speaking of a "full" closed cooling, vs. a "half" closed cooling. The difference as I understand, is that in a full system, the manifold is circulating coolant instead of raw water, and in a half system, the entire manifold, riser, and elbow are raw water. The way to tell is where the raw water is introduced to the exhaust, and whether the thermostat housing has 2 ports or 4. Mine is a half system (and always has been S/N OL395026 and 7), so there are no block off plates. Raw water is introduced at the bottom of the manifold, and circulates up the exhaust system to the elbow where it is mixed (too early in my opinion) with the exhaust. All of my gaskets are fully open, i.e. 4 slots, not 2 slots and to small holes (restrictor gasket). A Mercruiser bulletin recommended going to fully open quite a while back.

half closed cooling mercruiser.PNG
 
370Dancer said:
By block off plate, I assume you must be speaking of a "full" closed cooling, vs. a "half" closed cooling. The difference as I understand, is that in a full system, the manifold is circulating coolant instead of raw water, and in a half system, the entire manifold, riser, and elbow are raw water. The way to tell is where the raw water is introduced to the exhaust, and whether the thermostat housing has 2 ports or 4. Mine is a half system (and always has been S/N OL395026 and 7), so there are no block off plates. Raw water is introduced at the bottom of the manifold, and circulates up the exhaust system to the elbow where it is mixed (too early in my opinion) with the exhaust. All of my gaskets are fully open, i.e. 4 slots, not 2 slots and to small holes (restrictor gasket). A Mercruiser bulletin recommended going to fully open quite a while back.

View attachment 152473
Click to expand...
Okay.....that makes sense. Still, my commentary on the bolts loosening applies to either a half or full system. The pressure on the raw water side runs about 12 psi at 2,000 rpm. As it enters the exhaust manifold the pressure actually increases with the heat. The only escape it has is the riser ports which are restrictive.

Since the exact same exhaust manifolds and risers are used in both types of systems ....I would not be too quick to blame the riser design.

In my humble opinion a lot of "reversion" issues are actually the riser gaskets leaking internally. The casting of these parts and the associated machine work for the mating surfaces leaves a lot to be desired. Tom @ttmott would probably fire up his CNC machine to fix the surfaces......I use a flat file to get the surfaces as even as possible using a steel rule and feeler gauge to get it close. :)

I cannot stress enough that some of the surfaces have very little contact space between the cooling jacket and the exhaust port which leads to internal leaks if the bolts lose torque. In addition I have seen casting issues where there is pitting on the surface which also will create a problem over time. This is why I use Red Permatex to coat both sides of the gasket. I have never had one fail with this approach and using thread locker/lock washers.

I know sometimes we all start making things more complicated than they are when we chase a problem. I'm guilty of it too. I don't believe you have a design problem with the risers at this point other than they leaked. Get the redone heads on and let's get both engines working!
 
PlayDate said:
Okay.....that makes sense. Still, my commentary on the bolts loosening applies to either a half or full system. The pressure on the raw water side runs about 12 psi at 2,000 rpm. As it enters the exhaust manifold the pressure actually increases with the heat. The only escape it has is the riser ports which are restrictive.

Since the exact same exhaust manifolds and risers are used in both types of systems ....I would not be too quick to blame the riser design.

In my humble opinion a lot of "reversion" issues are actually the riser gaskets leaking internally. The casting of these parts and the associated machine work for the mating surfaces leaves a lot to be desired. Tom @ttmott would probably fire up his CNC machine to fix the surfaces......I use a flat file to get the surfaces as even as possible using a steel rule and feeler gauge to get it close. :)

I cannot stress enough that some of the surfaces have very little contact space between the cooling jacket and the exhaust port which leads to internal leaks if the bolts lose torque. In addition I have seen casting issues where there is pitting on the surface which also will create a problem over time. This is why I use Red Permatex to coat both sides of the gasket. I have never had one fail with this approach and using thread locker and lock washers.

I know sometimes we all start making things more complicated than they are when we chase a problem. I'm guilty of it too. I don't believe you have a design problem with the risers at this point other than they leaked. Get the redone heads on and let's get both engines working!
Click to expand...
All parts are here. Clean up time, then bolt up time.......
I'll follow your lockwasher/Permatex reco.
 
Question.
In this pic, you see the baffle? that is in the valley, below the intake manifold.
This piece of tin acts like it wants to be installed PRIOR to putting the heads on.
Or, do you just keep bending it until it goes back into place? Or, do you throw it away? There is no diagram that I can find from Mercury, marineengine.com, or others that even show it, much less call it out with a part number.
Can I just leave this out, or is it a big deal?
baffle.jpeg
 
370Dancer said:
Question.
In this pic, you see the baffle? that is in the valley, below the intake manifold.
This piece of tin acts like it wants to be installed PRIOR to putting the heads on.
Or, do you just keep bending it until it goes back into place? Or, do you throw it away? There is no diagram that I can find from Mercury, marineengine.com, or others that even show it, much less call it out with a part number.
Can I just leave this out, or is it a big deal?
View attachment 153345
Click to expand...
That baffle keeps hot oil off the underside of the intake manifold. It should deflect enough to pop in.
 
Confirmed with Innovation Marine. The tabs do catch the face of the intake, and the proper gasket has cut outs for them. Push rods and rockers on today, intake tomorrow, then bolt on fun........
valley pan in right.jpeg
 
ok, front stuff on. Installed valve covers, good. Now exhaust manifolds.
BRAND NEW OEM HEADS.
One of the bolt holes for the #5 exhaust manifold is STRIPPED!
I don't cross thread. I always hand thread my bolts to make sure I have at least 3 rows in before adding any tools. All other bolts good to go. 35ftlbs. This one, stripped at about 13.
So, what am I doing? Helicoil? Time-Sert? 45 slugs in the bottom of the hull?
Outboard side, of course, next to the gas tank. May or may not have room to drill out in place. I sure as SHIT don't want to have to pull the intake, and then the head.
Now that I've vented, I will try a longer bolt to see if there's room to get a bite.
 
370Dancer said:
ok, front stuff on. Installed valve covers, good. Now exhaust manifolds.
BRAND NEW OEM HEADS.
One of the bolt holes for the #5 exhaust manifold is STRIPPED!
I don't cross thread. I always hand thread my bolts to make sure I have at least 3 rows in before adding any tools. All other bolts good to go. 35ftlbs. This one, stripped at about 13.
So, what am I doing? Helicoil? Time-Sert? 45 slugs in the bottom of the hull?
Outboard side, of course, next to the gas tank. May or may not have room to drill out in place. I sure as SHIT don't want to have to pull the intake, and then the head.
Now that I've vented, I will try a longer bolt to see if there's room to get a bite.
Click to expand...
I have had great success with using a tap in this situation. Usually it is only the first few threads that get screwed up due to an old bolt. Line it up (use a long bolt in the adjoining bolt hole as a line up guide) and slowly turn it into the offending bolt hole. With some luck you will be back in business.

Use some wd40 as a lubricant.
 
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