I have a 2011 Mercruiser 5.0 MPI with Catalyst manifolds. Since the rear oxygen sensors rotted away every 18 months and threw an alarm I eliminated them with the CPI module. It simulates the rear oxygen sensors so your PCM doesn't throw a code. The rear O2 sensors only purpose in life is to tell the PCM if the catalyst are working. I use the CPI simulator since I am on a private lake and it has worked flawlessly. I also removed Catalyst cartridges. Result was no pinging using 87 Octane prior to that I had to use 89 octane. Even though my engine has tons of sensors Mercruiser eliminated the knock sensors on my model. I gained about 3 mph on top end. Exhaust doesn't stink like a skunk anymore.
Option 1 - Existing manifolds are 10 years old with 225 hours. Cost to replace manifolds and risers with Mercruiser catalyst style is $2K. I do the labor. Cat manifolds weigh 74lbs vs 43lbs for old style.
Options 2- Eliminate Cat manifolds and revert to traditional dry joint manifolds and risers. Barr manifold/riser kit with all hardware and gaskets delivered to my house $1k. I would have to buy a new thermostat housing used on eBay $150. Two new thermostat to riser hoses $70, new exhaust elbow from riser to rubber bellows used $150, drill and tap new manifolds for pre cat O2 sensor -free or buy space plates $100. So let say first time $1500. Note if I didn't have CPI simulator it would be another $450 so I am back at cost for Cat Manifolds. I could possible use my thermostat and riser hoses with modification. Taking a little chance flow could be different that would save$150. Pretty easy to try so if temps get high I can always go back and get different thermostat.
As far as manifold history my 1988 3.0 liter went 12 years before failing. Easily 500 hrs run time. First set failed back side of exhaust passage. Second set I replaced at 10 years with Barr manifolds and when broke apart could have gone another 10 years. Second set probably had half the hours as first set. That is when we starting drinking instead of sking. Salt to brackish water. Flushed with freshwater after every single use.
My buddies 350 Mag went 10 years and 245 hours. Manifold cracked externally at corner, When I broke apart again back side of exhaust passages looked good, it just accumulated sediment in corner and I assume overheated. Flushed with freshwater after every single use.
One key difference between Catalyst manifolds and traditional style is they are smooth, no corners and weigh twice what traditional manifolds weigh. I found where Mercruiser warrants new Catalyst manifolds 3 years or 475 hours.
My opinion is hours kills manifolds not age. Its the heat affecting vulnerable area just behind the exhaust passage where exhaust gas at 700F are hitting cast iron with 160F water is cooling on the opposite resulting in erosion corrosion.
It's painful there isn't a reliable way to determine manifold condition without use of sledge hammer. It's painful to spend $2K on manifolds which may be good for another 10 years. Its painful to loose a perfectly good engine due to a manifold failure. Ultrasonic testing isn't valid on cast materials due to the variable in castings.
In the end I go 10 years before changing manifolds. So $500 over 10 years isn't much savings, next change would save $1K if converted.
Resale value is important. If I convert I am sure some snowflake shop will tell the potential owner all the bs. In reality I would have done them a huge favor converting to traditional manifolds. I can sell the cats in my attic for probably $600 for set. Now if anyone ever has to replace catalyst you are forced to convert as the catalyst are $1200 each.
If you haven't figured it out yet Catalyst killed the sterndrive engines due to the increased cost. That is why all you see now is outboards BUT rumor is they are required to have catalyst in the near future....
1) So what would you do convert now for $1500 possible affecting resale value. In addition traditional manifolds weigh half as much so they not last as long as the catalyst manifolds. I haven't heard of any catalyst manifolds failing yet, I heard of a lot of catalyst cartridges in big blocks failing but not the manifolds.
2) Pay $2K worth of manifolds now. Looking at the design I feel risk are greatly reduced with just manifold replacement and not riser. Risers contain a fraction of the water as manifold and if it were to leak i don't think its possible it could hydrolock the engine. if fails during running engine pressure keep water going out boat. Save $1k by not replacing risers.
3)Do nothing, temperatures are good, assume if Mercrusier was warranting for 475 hours wait until 350 hours and reevaluate.
Option 1 - Existing manifolds are 10 years old with 225 hours. Cost to replace manifolds and risers with Mercruiser catalyst style is $2K. I do the labor. Cat manifolds weigh 74lbs vs 43lbs for old style.
Options 2- Eliminate Cat manifolds and revert to traditional dry joint manifolds and risers. Barr manifold/riser kit with all hardware and gaskets delivered to my house $1k. I would have to buy a new thermostat housing used on eBay $150. Two new thermostat to riser hoses $70, new exhaust elbow from riser to rubber bellows used $150, drill and tap new manifolds for pre cat O2 sensor -free or buy space plates $100. So let say first time $1500. Note if I didn't have CPI simulator it would be another $450 so I am back at cost for Cat Manifolds. I could possible use my thermostat and riser hoses with modification. Taking a little chance flow could be different that would save$150. Pretty easy to try so if temps get high I can always go back and get different thermostat.
As far as manifold history my 1988 3.0 liter went 12 years before failing. Easily 500 hrs run time. First set failed back side of exhaust passage. Second set I replaced at 10 years with Barr manifolds and when broke apart could have gone another 10 years. Second set probably had half the hours as first set. That is when we starting drinking instead of sking. Salt to brackish water. Flushed with freshwater after every single use.
My buddies 350 Mag went 10 years and 245 hours. Manifold cracked externally at corner, When I broke apart again back side of exhaust passages looked good, it just accumulated sediment in corner and I assume overheated. Flushed with freshwater after every single use.
One key difference between Catalyst manifolds and traditional style is they are smooth, no corners and weigh twice what traditional manifolds weigh. I found where Mercruiser warrants new Catalyst manifolds 3 years or 475 hours.
My opinion is hours kills manifolds not age. Its the heat affecting vulnerable area just behind the exhaust passage where exhaust gas at 700F are hitting cast iron with 160F water is cooling on the opposite resulting in erosion corrosion.
It's painful there isn't a reliable way to determine manifold condition without use of sledge hammer. It's painful to spend $2K on manifolds which may be good for another 10 years. Its painful to loose a perfectly good engine due to a manifold failure. Ultrasonic testing isn't valid on cast materials due to the variable in castings.
In the end I go 10 years before changing manifolds. So $500 over 10 years isn't much savings, next change would save $1K if converted.
Resale value is important. If I convert I am sure some snowflake shop will tell the potential owner all the bs. In reality I would have done them a huge favor converting to traditional manifolds. I can sell the cats in my attic for probably $600 for set. Now if anyone ever has to replace catalyst you are forced to convert as the catalyst are $1200 each.
If you haven't figured it out yet Catalyst killed the sterndrive engines due to the increased cost. That is why all you see now is outboards BUT rumor is they are required to have catalyst in the near future....
1) So what would you do convert now for $1500 possible affecting resale value. In addition traditional manifolds weigh half as much so they not last as long as the catalyst manifolds. I haven't heard of any catalyst manifolds failing yet, I heard of a lot of catalyst cartridges in big blocks failing but not the manifolds.
2) Pay $2K worth of manifolds now. Looking at the design I feel risk are greatly reduced with just manifold replacement and not riser. Risers contain a fraction of the water as manifold and if it were to leak i don't think its possible it could hydrolock the engine. if fails during running engine pressure keep water going out boat. Save $1k by not replacing risers.
3)Do nothing, temperatures are good, assume if Mercrusier was warranting for 475 hours wait until 350 hours and reevaluate.
