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?

Did the previous impeller go to pieces that are now obstructing some passages?

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.

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.

i will double check that.

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..

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.

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Port side hose attachments to the heat exchanger. large hose at bottom is sea water in. Smaller hose is exit to exhaust manifold.

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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.

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..

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.

Some shops hire mechanics and others hire parts replacers. Most likely a good move taking the boat to another shop. It's not that hard to start loosening hoses and flush them out until you notice a blockage.

very very true

SO guys.. I moved it to a new shop as stated above because I just didn't think the manifolds were clogged because this boat is so damn clean.. I just got a call from the shop and guess what....... it was a 35 to 40 dollar part.. it was a check valve that is used for the garden hose connection inside the engine area for flushing.. SO what happen with it.. it looks like the check valve that opens (which closes the drive side) when flushing with the hose DID NOT release when I finished using the hose. I didn't even know there was piece even like this, its in line from the hose coming from the transom to the water pump.. its a easy fix / replacement but DAMN that other shop for not finding this and wanting to charge me 3000 dollars for manifolds and install...

Maybe a dumb question but... Was the Manifold problem discussed a 496HO only problem or both 496 and 496HO problem? I'm looking at 496 boats and wonder if this is something I should keep an eye out for?

Which "problem?" If you mean that the motors were originally sold with aluminum manifolds and they went to cast iron after '05 or so, that's both the base and HO I believe.

That said, I don't think it's a problem at all. If you have either, I'd run them until it's time to replace, then buy Stainless Marine.

If you mean the check valve that stuck in this case, that's gotta be both as well. Not a big deal, just sounds like an incompetent and/or unscrupulous shop.

this boat you can eat off these engines and that is why I could not believe it was a manifold problems.. I did talk to Merc hotline # and they did some what know of the problems from the older manifolds because that's why they changed the material they are made in .

yes it was the shop just trying to make a easy buck. I will keep using these manifolds until the real problem pops up with them.

The check-valve Tee-connection that Baja factory installs in their boats is JUNK. I do not know why they put it in there. I've seen and heard of so many boats having problems with it.

You DO NOT need the spring loaded check ball valve in there. Take it apart and remove the ball/spring.

When you have the flush fitting, with no check ball; as soon as your turn on the hose, it will backflush from the Tee-fitting backwards out the drive. (Important!)
As soon as you start the motor, the SWP will pull the water in, and you will see little to no water coming out the drive.
Turn the engine off, and then let it flush backwards for a bit longer.



Additionally, I feel as though when they have this check-ball Tee connection in there, and it DOESN'T flush rearward out the drive, I think this is a DIRECT contributor to some salt water boats which have a transom assembly corrosion problem in the water supply hose and associated. I've seen THIS problem with Bajas before too.

yup that was the part.. I couldn't believe it, the one we put in there now is used on the volvo motors and its a metal y fitting .

Port side riser overheats
 

Hi guys looking for some help here. 496ho overheats in port side manifold. Checked it with a heat gun. New impeller and still over heats at WOT and goes into guardian mode .... cools back down at idle. Never had a impeller break off. Back flushed it..good flow from both exhaust at idle and while getting up to plane ..... pressures are good , Check with scan tool.

pulled hoses off from the closed cooling system and back-flushed every thing separate from the fuel cooler, oil cooler, power steering cooler ext...... is it possible for the ball check valve to be stuck ...... water flow is good I’m just wondering if the water leaving the heat exchanger is some how recirculating the hot water back in though the oil cooler. Is this possible .... could really use the help

Check/ remove the end caps on the main heat exchanger to check the rubber cap seals and than the oil cooler for debris, on the port side under exhaust manifold, for clog.

Change the rubber seals on each end of the heat exchanger,when they get old they can get stretched and can block the flow of water through the heat exchanger

Forgot to mention that I already changed the gaskets on the sides of the heat exchanger..... ordered a new T drain with the ball check valve .... I will put it next week and see what happens...... talk to the parts guy and they no longer sell the parts to rebuild it .... had to buy the whole part for $52 ... in update as I go

You can pull both hoses from the manifold with the engine running to see how much flow and if the ball valve is working.Dont run for to long with no water going through the manifold

Flush it with 80% water 20% muriatic maybe you have some calcium/salt buildup.