496ho manifolds
08-27-2016, 11:17 AM
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496ho manifolds
SO get this.. shop installed the new hardin pump and pulled the old one off.. the old pump and impeller was brand new, not a single problem or wear marks. SO.. they started the boat up ( I was there and observed) after flushing all hoses and heat exchanger.. anyway, the boat did the same ****, the water coming out the pipes was little to none. the tech pulled a sensor and you could see the water pump was pushing major pressure but it wasn't coming out the back. we started feeling around and you could feel that the right side exhaust elbow riser was getting way hot and the left raiser was hot also but not as bad.
they input was that the manifold must be blocking the flow. SO they state that I will have to replace the manifolds with new style.. this boat shows NO salt water use and i'm just shaking my head.. boat has 270hrs.
any input guys with this type of problems?
they input was that the manifold must be blocking the flow. SO they state that I will have to replace the manifolds with new style.. this boat shows NO salt water use and i'm just shaking my head.. boat has 270hrs.
any input guys with this type of problems?
08-28-2016, 08:03 AM
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Sounds like a place to start. I doubt very much something make it all the way to the exhaust manifold (s) to create a blockage. Maybe the power steering, oil, or even cool fuel cooler could have a blockage with old impeller pieces. The heat exchanger is a likely place as well if they made it that far. But to just replace a $500 exhaust manifold sounds crazy. I've never heard of this. The only reason they are hot is because of the lack of water flowing to them, not because they are blocked. Best of luck. Maybe find a different shop to take a look at it.
08-28-2016, 08:02 PM
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I'm sure you ruled this out, but do you have Captain's Call? I once had a voltage situation causing my port motor captain's call to not activate. The result was very little water coming out of the exhaust. I thought it was the water pump until I realized the solenoid was not throwing the levers. I moved the levers manually and bingo, water from the exhaust.
08-29-2016, 09:08 AM
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I'm sure you ruled this out, but do you have Captain's Call? I once had a voltage situation causing my port motor captain's call to not activate. The result was very little water coming out of the exhaust. I thought it was the water pump until I realized the solenoid was not throwing the levers. I moved the levers manually and bingo, water from the exhaust.
08-29-2016, 09:10 AM
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I just got a lovely letter back from Merc about my manifolds..
it states.. YES your motor has the Alum manifolds that have now be changed due to a redesign to cast irons.. have a good day and fun on the water lol..
it states.. YES your motor has the Alum manifolds that have now be changed due to a redesign to cast irons.. have a good day and fun on the water lol..
08-30-2016, 08:40 AM
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I've got aluminum manifolds with no issues. I would not change them unless they are leaking. There is no way for them to be blocked (well, there is always a way but it is not likely).
The first thing to check is to make sure (as has already been suggested) that there is no obstruction in the raw water lines. This almost always occurs at the oil cooler as the power steering cooler (the first cooler in line and mounted to the rear of the engine above coupler) is just a large tube. The oil cooler has many small tubes running through it and this will catch just about anything from seaweed to sea shells to old impeller parts. You can back flush the entire system by removing the hose from the outlet of the raw water pump (a pain) or the intake of the ps pump (still a pain but not as bad). Next remove the large hose on the bottom port side of the heat exchanger and stick a water hose in here. Turn the water on and see what you get out (try to catch the water coming out in a bucket etc. so you can determine if anything came out. You should get unobstructed water flow.
If that all looks good you can continue to remove hoses and verify you get water flow out the exhaust to determine where the blockage is. It may be at the heat exchanger itself but usually the oil cooler catches most of the crud.
Of course the primary thing to remember if you have an exhaust diverter (captains call) is that the water will flow down and out the exhaust tube at the drive, not out the transom, even with the exhaust open. The water is just not moving fast enough to bridge that big exhaust opening in the bottom of the diverter. You can get a heat gun to make sure the exhaust is getting as hot as you believe.
If you are now convinced that you still do not have water flowing, then there is one other thing to check. On the bottom of the manifolds is a check valve that is part of the drain system (that you activate with the air pump). These can corrode over time and block the water flow. Remove the hose going into the bottom of the manifold or water rail and make sure that is open.
If you decide you want to get rid of your aluminum manifolds, you will have lots of takers for them!
New nipples installed on water rail. Drain is below that.
[ATTACH=CONFIG]558878[/ATTACH]
Port side hose attachments to the heat exchanger. large hose at bottom is sea water in. Smaller hose is exit to exhaust manifold.
[ATTACH=CONFIG]558879[/ATTACH]
The first thing to check is to make sure (as has already been suggested) that there is no obstruction in the raw water lines. This almost always occurs at the oil cooler as the power steering cooler (the first cooler in line and mounted to the rear of the engine above coupler) is just a large tube. The oil cooler has many small tubes running through it and this will catch just about anything from seaweed to sea shells to old impeller parts. You can back flush the entire system by removing the hose from the outlet of the raw water pump (a pain) or the intake of the ps pump (still a pain but not as bad). Next remove the large hose on the bottom port side of the heat exchanger and stick a water hose in here. Turn the water on and see what you get out (try to catch the water coming out in a bucket etc. so you can determine if anything came out. You should get unobstructed water flow.
If that all looks good you can continue to remove hoses and verify you get water flow out the exhaust to determine where the blockage is. It may be at the heat exchanger itself but usually the oil cooler catches most of the crud.
Of course the primary thing to remember if you have an exhaust diverter (captains call) is that the water will flow down and out the exhaust tube at the drive, not out the transom, even with the exhaust open. The water is just not moving fast enough to bridge that big exhaust opening in the bottom of the diverter. You can get a heat gun to make sure the exhaust is getting as hot as you believe.
If you are now convinced that you still do not have water flowing, then there is one other thing to check. On the bottom of the manifolds is a check valve that is part of the drain system (that you activate with the air pump). These can corrode over time and block the water flow. Remove the hose going into the bottom of the manifold or water rail and make sure that is open.
If you decide you want to get rid of your aluminum manifolds, you will have lots of takers for them!
New nipples installed on water rail. Drain is below that.
[ATTACH=CONFIG]558878[/ATTACH]
Port side hose attachments to the heat exchanger. large hose at bottom is sea water in. Smaller hose is exit to exhaust manifold.
[ATTACH=CONFIG]558879[/ATTACH]
08-30-2016, 09:46 AM
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Ditto the above comments.
It should be possible to pull the manifolds/manifold -connections and test them for flow.
Should also be possible to pull the input to the manifolds and see what's getting to them.
Where is the water pressure measured? If something is mostly blocked off downstream of the pump and sensor, I'd expect exactly what you're seeing.
You said the impeller is brand new. Do you know what happened to the prior impeller? Did it fail? Did it come out in pieces, or did the shop pull it and never show it to you?
Not sure the 270 hours say much. They're probably what, 10 -12 years old with as many seasons in the brackish Bay water. Maybe they're badly corroded. Regardless, flow testing should tell a lot, to isolate where the apparently-good pressure from the pump isn't delivering enough waterr downstream.
It should be possible to pull the manifolds/manifold -connections and test them for flow.
Should also be possible to pull the input to the manifolds and see what's getting to them.
Where is the water pressure measured? If something is mostly blocked off downstream of the pump and sensor, I'd expect exactly what you're seeing.
You said the impeller is brand new. Do you know what happened to the prior impeller? Did it fail? Did it come out in pieces, or did the shop pull it and never show it to you?
Not sure the 270 hours say much. They're probably what, 10 -12 years old with as many seasons in the brackish Bay water. Maybe they're badly corroded. Regardless, flow testing should tell a lot, to isolate where the apparently-good pressure from the pump isn't delivering enough waterr downstream.
Last edited by Ghost24; 08-30-2016 at 09:56 AM.
09-01-2016, 07:53 AM
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thanks guys.. I'm working so much that I don't have time to do it myself.. BUT I did move the boat to another shop last night.. I just didn't feel right with their outcome.. the new shop is going to look for a clog in the system FIRST before even looking at removing and replace the manifolds..
09-03-2016, 02:32 PM
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There's a fitting in the transom assembly that implodes restricting water flow and alows air into the sea water pump. Follow the inlet hose to the transom, there's a 45° fitting held by 2 bolts, pull the 45 and look at the fitting that attaches to the 5/8" rubber hose to the drive. Mine was bad by 09 on an 05 boat. I did away with it and went with a transom pickup to a Gil strainer. The way the closed cooling in designed on the 496, it's always gonna favor the starboard side since that's the direction of flow.
