S
shoremike
Guest
I have been told by a friend that the risers should be replaced every four years. Another friend indicated 7 to eight years. Which is it? It is a 240 sundancer 2001.
G
Guest
Guest
Depends on several things. Length of service(actual use) Type of use - Salt/fresh water and pre-emptive maintanance. If you periodicly pull, clean them up and paint fog the interior they will last longer. I Have seen them gone in 3 years and still working over 5 years.
tansundancer
New Member
- Feb 5, 2005
- 3
Does a closed cooling system make the risers last much longer?
MichaelNJ
New Member
Just Pulled mine
I pulled one of my risers from the manifold the other day. This is the end of the fifth season for my boat. I have twin 5.0 MPI's woth 305 hours, raw water cooled in salt water all season with no flushing.
The riser, elbow and manifold looked fine from what I could see. There was just some surface rust on the outside.
In the spring, I will pull all four and check again. I also plan to wire brush the outside and repaint them. I know that's just cosmetic. How can you paint the water jacket inside though? How do you clean it so the paint will stick?
How do you know when they need to be changed short of them being rusted through? What so you look for?
I pulled one of my risers from the manifold the other day. This is the end of the fifth season for my boat. I have twin 5.0 MPI's woth 305 hours, raw water cooled in salt water all season with no flushing.
The riser, elbow and manifold looked fine from what I could see. There was just some surface rust on the outside.
In the spring, I will pull all four and check again. I also plan to wire brush the outside and repaint them. I know that's just cosmetic. How can you paint the water jacket inside though? How do you clean it so the paint will stick?
How do you know when they need to be changed short of them being rusted through? What so you look for?
I will pass along what I have read on the old forum.
First, the riser is the vertical exhaust extension that may or may not be present, depending on how your boat is constructed. The elbow is the top component, where the exhaust makes a 90 degree turn, and cooling water is added into the exhaust flow.
In a fresh water cooled system, the riser may be raw water cooled or fresh water cooled, depending on if it is a 'half system' or 'full system' respectively. The elbow is always raw water cooled, because that is where the sea water used for cooling either system is added into the exhaust flow.
From what I have read before, the main failiure mode is with corrosion from the inner exhaust passage outward towards the water passage. It is not corrosion from the water passages themselves. When the exhaust passage corrodes into the water passage, then you have a failure.
Corrosion happens primarily when the boat is sitting in the water and not running. Then you have a closed air system, with seawater closing off the exhaust. There is always water present at the water level, and so the humidity in the exhaust passages will go towards 100 percent. If is it real sea water, then you get the added effect of the salt corrosion. So just having your boat sit in salt water is the worst case. Having it running obviously will dry out the exhaust, as will having it out of the water.
Here is a picture of the gasket surface view of my elbow on the left and riser on the right from my 7.4L engine. As far as I know, these are original 1996 parts, but I don't know that for sure. You can see in the pictures there is little to no real loss of metal on the inner exhaust passages. There is some flaking in the water passage, but not serious.
Oops, sorry, I see that the old gasket is still attached to the riser surface. I can tell by the small hole in the gasket. The riser has a full slot here behind the small hole.
First, the riser is the vertical exhaust extension that may or may not be present, depending on how your boat is constructed. The elbow is the top component, where the exhaust makes a 90 degree turn, and cooling water is added into the exhaust flow.
In a fresh water cooled system, the riser may be raw water cooled or fresh water cooled, depending on if it is a 'half system' or 'full system' respectively. The elbow is always raw water cooled, because that is where the sea water used for cooling either system is added into the exhaust flow.
From what I have read before, the main failiure mode is with corrosion from the inner exhaust passage outward towards the water passage. It is not corrosion from the water passages themselves. When the exhaust passage corrodes into the water passage, then you have a failure.
Corrosion happens primarily when the boat is sitting in the water and not running. Then you have a closed air system, with seawater closing off the exhaust. There is always water present at the water level, and so the humidity in the exhaust passages will go towards 100 percent. If is it real sea water, then you get the added effect of the salt corrosion. So just having your boat sit in salt water is the worst case. Having it running obviously will dry out the exhaust, as will having it out of the water.
Here is a picture of the gasket surface view of my elbow on the left and riser on the right from my 7.4L engine. As far as I know, these are original 1996 parts, but I don't know that for sure. You can see in the pictures there is little to no real loss of metal on the inner exhaust passages. There is some flaking in the water passage, but not serious.
Oops, sorry, I see that the old gasket is still attached to the riser surface. I can tell by the small hole in the gasket. The riser has a full slot here behind the small hole.
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Here is a picture of the top of the manifold of my 7.4L. What you are looking for is to make sure there is still plenty of metal left between the exhaust and the water passage. In this view, I don't detect and real loss of metal from the exhaust passage.
Also below is a closeup of the manifold top, where you can see the thickness between the interior exhaust area and the water passage.
What you definitely don't want is any way for the coolant to get by the gasket and into the exhaust passage. If it does, it will dump down towards the exhaust valves, and into the cylinders if it can. So make sure it is not corroding at the gasket surface, and the you have a good clean solid surface to hold the new gasket in place, sealing the water passages.
Also below is a closeup of the manifold top, where you can see the thickness between the interior exhaust area and the water passage.
What you definitely don't want is any way for the coolant to get by the gasket and into the exhaust passage. If it does, it will dump down towards the exhaust valves, and into the cylinders if it can. So make sure it is not corroding at the gasket surface, and the you have a good clean solid surface to hold the new gasket in place, sealing the water passages.
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Captain Don
Member
Manifolds and Elbows
Dave, a question, after looking at your Pic's, I also have 7.4L's. My manifolds are Fresh Water Cooled, my elbows are Raw Water, I just replaced all four, they were on for 7 years, I never overheated, ran at 145, I figured I would change them before I had to do it. My gaskets old and new have no holes in them at all, they are completely blocked off. The old gaskets were the metal with the gasket coating. The new gaskets are some type of a composite, fiber, or graphite, no metal at all. I was told they are better because the salt water cannot eat through and get into the manifold.
My question is why does your gasket have small holes, can't salt water get through? Does it have to do with Risers between the elbow and Manifold? I do not have Risers. I would be interested to know. Thanks
Dave, a question, after looking at your Pic's, I also have 7.4L's. My manifolds are Fresh Water Cooled, my elbows are Raw Water, I just replaced all four, they were on for 7 years, I never overheated, ran at 145, I figured I would change them before I had to do it. My gaskets old and new have no holes in them at all, they are completely blocked off. The old gaskets were the metal with the gasket coating. The new gaskets are some type of a composite, fiber, or graphite, no metal at all. I was told they are better because the salt water cannot eat through and get into the manifold.
My question is why does your gasket have small holes, can't salt water get through? Does it have to do with Risers between the elbow and Manifold? I do not have Risers. I would be interested to know. Thanks
I assume you are referring to the two small holes, one at the bottom and one at the top of the picture. Yes, they let water through the same as the slots in the sides of the gasket do. The water jacket in the riser is a single chamber internally, I suspect here Merc is just trying to control the flow of water. I don't know the reason, whether it is where it flows or an atttempt to control volume of flow. I don't think Merc was consistent with the placement of these holes over the years.
The pictures above were taken when my boat did not have fresh water cooling. In that case, water from the thermostat housing enters the bottom of the exhaust manifold, flows up through the first gasket into the riser, then up through the second gasket into the elbow. From there it gets dumped into the exhaust stream. So in this case, all gaskets have to be ported to allow water flow.
Then when I added fresh water cooling, a solid gasket had to be used at the point that separates engine coolant and sea water cooling. In my case, that is between the riser and the elbow.
Pictures follow.
The pictures above were taken when my boat did not have fresh water cooling. In that case, water from the thermostat housing enters the bottom of the exhaust manifold, flows up through the first gasket into the riser, then up through the second gasket into the elbow. From there it gets dumped into the exhaust stream. So in this case, all gaskets have to be ported to allow water flow.
Then when I added fresh water cooling, a solid gasket had to be used at the point that separates engine coolant and sea water cooling. In my case, that is between the riser and the elbow.
Pictures follow.
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Re: Manifolds and Elbows
I think Merc has tried different thermostats in different cases too. My boat has a 160 degree thermostat, and the engine typically runs at or just below 170. I prefer not to run an engine at 145, I think it is too cool, and you will get more wear. I believe the reason to run that temp though, is to prevent salt in salt water from crystallizing in the engine. I think this is supposed to happen at about 160 degrees, and can build up and block cooling passages.
Since you have closed cooling, I would think you could run a hotter thermostat if you wished. You don't have salt water in the engine block.
That sounds reasonable to me. I have only seen composite gaskets.
Dave
Captain Don said:
I think Merc has tried different thermostats in different cases too. My boat has a 160 degree thermostat, and the engine typically runs at or just below 170. I prefer not to run an engine at 145, I think it is too cool, and you will get more wear. I believe the reason to run that temp though, is to prevent salt in salt water from crystallizing in the engine. I think this is supposed to happen at about 160 degrees, and can build up and block cooling passages.
Since you have closed cooling, I would think you could run a hotter thermostat if you wished. You don't have salt water in the engine block.
Captain Don said:
That sounds reasonable to me. I have only seen composite gaskets.
Dave
Captain Don
Member
Dave, thanks for the reply and info. When I purchased the boat in 2000, it had a 145 in the port and a 160 in the starboard engines. I discovered this because the starboard engine always ran around 170, which I thought was much too high. I checked the engine manual, it called for 145 degree thermostats in both engines, so I changed them both to new 145's. How does a cooler engine get more ware than a hotter engine, I am fairly new at the mechanics of these engines, but I have never had a problem and still want to make the right decision. Please advise. Thanks again
Wow, you want real facts and not just someone's opinion? :smt013
Short answer, I don't know technically all the reasons. I could even be wrong! I have heard over and over that an engine gets most of its wear during the first few minutes it is operated, and when it is up to temp, wear is greatly reduced. OK, here is a link:
http://www.carnut.com/ramblin/_cool3.html
In my diesel truck with the Cummins engine, it specifically states NOT to let the engine idle for long periods of time like you used to see truckers do, and especially in cold weather. The reason is the engine uses very little fuel at idle and cannot keep itself warm. In a diesel engine, you get some fuel wash by the rings and into the crank case. This fuel contains sulfur. You also will get moisture into the engine crank case. Water and sulfur make sulfuric acid.
So you want you engine to be hot enough to boil out any moisture. I think this applies whether the engine is gas or diesel. Per the link above, 170 degrees is just barely warm enough to do this.
When I bought my boat (used), it had raw water cooling and a 160 degree thermostat. It would not heat up to 170 unless on plane. After installing the fresh water cooling it will heat up to at least 160 without having to go on plane.
Short answer, I don't know technically all the reasons. I could even be wrong! I have heard over and over that an engine gets most of its wear during the first few minutes it is operated, and when it is up to temp, wear is greatly reduced. OK, here is a link:
http://www.carnut.com/ramblin/_cool3.html
In my diesel truck with the Cummins engine, it specifically states NOT to let the engine idle for long periods of time like you used to see truckers do, and especially in cold weather. The reason is the engine uses very little fuel at idle and cannot keep itself warm. In a diesel engine, you get some fuel wash by the rings and into the crank case. This fuel contains sulfur. You also will get moisture into the engine crank case. Water and sulfur make sulfuric acid.
So you want you engine to be hot enough to boil out any moisture. I think this applies whether the engine is gas or diesel. Per the link above, 170 degrees is just barely warm enough to do this.
When I bought my boat (used), it had raw water cooling and a 160 degree thermostat. It would not heat up to 170 unless on plane. After installing the fresh water cooling it will heat up to at least 160 without having to go on plane.
Captain Don
Member
Dave, thank you for your opinion, I appreciate all the information you have given me, I'm still learning about this.
According to my Clymer manual, which covers 1995-1997, here are the numbers for the 454 engine:
1995 RWC Carb 143 F
1995 RWC FI 160 F
1995 FWC 140 F
1996 All 160 F
1997 All 160 F
Does not agree with my theory about RWC vs FWC and salt water at all. Maybe someone else can add more here.
1995 RWC Carb 143 F
1995 RWC FI 160 F
1995 FWC 140 F
1996 All 160 F
1997 All 160 F
Does not agree with my theory about RWC vs FWC and salt water at all. Maybe someone else can add more here.
