Anonymous
01-22-2003, 10:14 PM
Engineman
normal member in standard member. 1. Engine Heat Discussion
Hey all,
There is discussion at the bottom of the exhaust manifold section dealing with gaskets.
The OE gaskets have slots cut on 3 sides. This is important because the blank should go at the outlet end of the riser. This will direct the water flow through the long side of the riser and prevent the water from taking the shortcut.
Since PCM has designed their manifolds and risers for raw water cooling it is important to install the gaskets properly.
Also as mentioned before do not use silicone to seal these gaskets. Use something such as Permatex #2.
Date: 08:31 a.m. on 04-06-2001
Leprechaun
premium member in standard member. 2. Re:Engine Heat Discussion
Engineman - I never use the permatex, rather I soak my manifold/riser gaskets in fresh engine oil for a few days prior to installation. This is an effort to cut back on the surface erosion/corrosion of the manifold's gasket surface in case I have to change out the riser before the manifold is due. Plus the Permatex is a PITA to clean up when changing the risers only. What do you think of this idea and do you feel the Permatex would be better? Rgds, Leprechaun
Date: 09:07 a.m. on 04-06-2001
capt_D
normal member in standard member. 3. Re:Engine Heat Discussion
Leprechaun, how often do you change the risers, and why don't you change the manifolds as often? I asume you are raw water cooled. Do you think the indmar parts are any better than the osco or others?
capt_D
Date: 11:26 a.m. on 04-06-2001
Leprechaun
premium member in standard member. 4. Re:Engine Heat Discussion
capt D - you will find that the manifolds last at least twice as long as the risers. This, I believe is because the manifolds are always full of water whereas the risers drain each time you stop the engine, thus exposing the wet water passages inside the riser to oxygen, thus accelerating their degradation. The problem is that there is inevitable leakage between the riser and manifold despite the gasket and this causes corrosion of the riser mounting surface on the manifold. In an attempt to slow this I've gone to oil-soaked gaskets. I'll get back to you in a year or so to report the results of my experiment. Really, the proper course of action would be to remove the manifolds and have a machine shop square up the gasket surface with a surface mill. And FYI my rig is FWC not RWC and the answer to your other question is that no, I don't see any difference in the quality or the wall casting thickness between Osco, Barr, Indmar or PCM manifolds. Rgds, Leprechaun
Date: 12:08 p.m. on 04-06-2001
capt_D
normal member in standard member. 5. Re:Engine Heat Discussion
Leprechaun, thanks for your answer but one thing you said has me confused. My last boat had FWC Crusader engines and the manifolds never needed replaced, just the risor and elbows. The manifolds had freshwater going through them. Are you saying you have a FWC engine with RWC manifolds?
capt_D
Date: 06:44 p.m. on 04-06-2001
Leprechaun
premium member in standard member. 6. Re:Engine Heat Discussion
capt D - there are two types of FWC systems. The "Full" system, which includes the exhaust manifolds in the FW side and the "Half" system which, of course, excludes the manifolds. Both types have their advantages, namely, in the Full closed system the manifolds last a good deal longer, not being exposed to corrosive Salt Water. This however adds greatly to the responsibility of the FW side to maintain proper temperature, the manifolds obviously generate a great deal of heat which has to be removed and carried to the heat exchanger, and thence to the RW side. The entire FW side has to be fully up to snuff to handle that extra load. Generally a larger heat exchanger is specified for these applications. Crusader is one manufacturer that offer this full closed cooling. Mercruiser also offers it as standard on their "Horizon" line as well as an option on their Magnum engines.
PCM (Pleasurecraft Marine) goes the other way. The reasoning there is that a half closed system puts MUCH less stress on the cooling system, excluding the manifolds as it does, and therefore the tendency to run "A bit hot" is somewhat minimized.
Both systems sre good, I probably, possibly, kinda, might lean toward the full system, as I'm a fanatic with my boat and flush and maintain my cooling system to standards that far exceed the manufacturer's recommendations. I just haven't had the opportunity to own a boat with a full closed system yet.
Maybe my next boat.
Who knows?
Rgds, Leprechaun
Date: 09:19 p.m. on 04-06-2001
capt_D
normal member in standard member. 7. Re:Engine Heat Discussion
Leprechaun, i agree with you that the full system tends to run hot if everything is not perfect. It is most noticeable here in Florida in the summer when the water temps are high. Another negative is too many hoses. I really like the simplicity of RWC. So, how often do you change your risors? "
You said the manifolds last twice as long."
capt_D
Date: 08:45 a.m. on 04-07-2001
Leprechaun
premium member in standard member. 8. Re:Engine Heat Discussion
Capt D - I only seem to get 2&1/2 years out of a set of risers and 5 or so out of Manifolds. This is because the boat sits all week with dampness in the risers, waiting for the next weekend. Ironically, if I got to run the boat more often, I believe I would get more life out of the exhaust. I understand that the average life expectancy of risers is about 4-5 years and around 7-8 for RWC manifolds.
Also, I tend to change the risers out BEFORE overheat problems arise, so maybe I might be able to go to 3&1/2 years on them. It just seems that the water passages are chock full o'rust when I pull them at the shortened interval, so rather than have 'em boiled out, I just chuck 'em. I'm deathly afraid of losing a riser offshore either to rust closure or even worse, rust-through. Nothing would ruin my day faster than a motor that hydra-locks offshore. That would be a major bummer... Rgds, Leprechaun
Date: 01:31 p.m. on 04-07-2001
normal member in standard member. 1. Engine Heat Discussion
Hey all,
There is discussion at the bottom of the exhaust manifold section dealing with gaskets.
The OE gaskets have slots cut on 3 sides. This is important because the blank should go at the outlet end of the riser. This will direct the water flow through the long side of the riser and prevent the water from taking the shortcut.
Since PCM has designed their manifolds and risers for raw water cooling it is important to install the gaskets properly.
Also as mentioned before do not use silicone to seal these gaskets. Use something such as Permatex #2.
Date: 08:31 a.m. on 04-06-2001
Leprechaun
premium member in standard member. 2. Re:Engine Heat Discussion
Engineman - I never use the permatex, rather I soak my manifold/riser gaskets in fresh engine oil for a few days prior to installation. This is an effort to cut back on the surface erosion/corrosion of the manifold's gasket surface in case I have to change out the riser before the manifold is due. Plus the Permatex is a PITA to clean up when changing the risers only. What do you think of this idea and do you feel the Permatex would be better? Rgds, Leprechaun
Date: 09:07 a.m. on 04-06-2001
capt_D
normal member in standard member. 3. Re:Engine Heat Discussion
Leprechaun, how often do you change the risers, and why don't you change the manifolds as often? I asume you are raw water cooled. Do you think the indmar parts are any better than the osco or others?
capt_D
Date: 11:26 a.m. on 04-06-2001
Leprechaun
premium member in standard member. 4. Re:Engine Heat Discussion
capt D - you will find that the manifolds last at least twice as long as the risers. This, I believe is because the manifolds are always full of water whereas the risers drain each time you stop the engine, thus exposing the wet water passages inside the riser to oxygen, thus accelerating their degradation. The problem is that there is inevitable leakage between the riser and manifold despite the gasket and this causes corrosion of the riser mounting surface on the manifold. In an attempt to slow this I've gone to oil-soaked gaskets. I'll get back to you in a year or so to report the results of my experiment. Really, the proper course of action would be to remove the manifolds and have a machine shop square up the gasket surface with a surface mill. And FYI my rig is FWC not RWC and the answer to your other question is that no, I don't see any difference in the quality or the wall casting thickness between Osco, Barr, Indmar or PCM manifolds. Rgds, Leprechaun
Date: 12:08 p.m. on 04-06-2001
capt_D
normal member in standard member. 5. Re:Engine Heat Discussion
Leprechaun, thanks for your answer but one thing you said has me confused. My last boat had FWC Crusader engines and the manifolds never needed replaced, just the risor and elbows. The manifolds had freshwater going through them. Are you saying you have a FWC engine with RWC manifolds?
capt_D
Date: 06:44 p.m. on 04-06-2001
Leprechaun
premium member in standard member. 6. Re:Engine Heat Discussion
capt D - there are two types of FWC systems. The "Full" system, which includes the exhaust manifolds in the FW side and the "Half" system which, of course, excludes the manifolds. Both types have their advantages, namely, in the Full closed system the manifolds last a good deal longer, not being exposed to corrosive Salt Water. This however adds greatly to the responsibility of the FW side to maintain proper temperature, the manifolds obviously generate a great deal of heat which has to be removed and carried to the heat exchanger, and thence to the RW side. The entire FW side has to be fully up to snuff to handle that extra load. Generally a larger heat exchanger is specified for these applications. Crusader is one manufacturer that offer this full closed cooling. Mercruiser also offers it as standard on their "Horizon" line as well as an option on their Magnum engines.
PCM (Pleasurecraft Marine) goes the other way. The reasoning there is that a half closed system puts MUCH less stress on the cooling system, excluding the manifolds as it does, and therefore the tendency to run "A bit hot" is somewhat minimized.
Both systems sre good, I probably, possibly, kinda, might lean toward the full system, as I'm a fanatic with my boat and flush and maintain my cooling system to standards that far exceed the manufacturer's recommendations. I just haven't had the opportunity to own a boat with a full closed system yet.
Maybe my next boat.
Who knows?
Rgds, Leprechaun
Date: 09:19 p.m. on 04-06-2001
capt_D
normal member in standard member. 7. Re:Engine Heat Discussion
Leprechaun, i agree with you that the full system tends to run hot if everything is not perfect. It is most noticeable here in Florida in the summer when the water temps are high. Another negative is too many hoses. I really like the simplicity of RWC. So, how often do you change your risors? "
You said the manifolds last twice as long."
capt_D
Date: 08:45 a.m. on 04-07-2001
Leprechaun
premium member in standard member. 8. Re:Engine Heat Discussion
Capt D - I only seem to get 2&1/2 years out of a set of risers and 5 or so out of Manifolds. This is because the boat sits all week with dampness in the risers, waiting for the next weekend. Ironically, if I got to run the boat more often, I believe I would get more life out of the exhaust. I understand that the average life expectancy of risers is about 4-5 years and around 7-8 for RWC manifolds.
Also, I tend to change the risers out BEFORE overheat problems arise, so maybe I might be able to go to 3&1/2 years on them. It just seems that the water passages are chock full o'rust when I pull them at the shortened interval, so rather than have 'em boiled out, I just chuck 'em. I'm deathly afraid of losing a riser offshore either to rust closure or even worse, rust-through. Nothing would ruin my day faster than a motor that hydra-locks offshore. That would be a major bummer... Rgds, Leprechaun
Date: 01:31 p.m. on 04-07-2001