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correct exhaust risers?

8

805HD

Regular Contributor
So my new barr risers/ exhaust elbows showed up today, they look the same but I am not convinced. The new ones have some sort of metal sleeve inside them. I also don't see any kind of internal passages like I do on the original ones. Also can someone explain to me why the manifolds and risers share identical porting on their mating surfaces just to be blocked off? Seems so backwards lol

Shes almost ready!

old left new right






I know I will have to swap over those brass fittings. I still don't fully understand this system, seems like water being sent to dead ends? lol Its looking like i didn't even need new risers to begin with and might be easier to just use the old ones and return the new ones?

thanks in advance!
 
The Barr risers are made a little different. The Mercruiser ones are fully cast, but the Barr ones have the mixing tube press fit into the casting. If you look at the Mercruiser one you see some convolutions in the outside of the exit tube which helps atomize the water as it comes out. The Barr one has a slight flare to the exhaust tube which does the same thing to the water...just breaks it up. The cooling water goes up the front of the riser to an opening where it exits just before the engine exhaust. The water and exhaust mix in the Y pipe and exit thru the hub of the prop. The vortex action of the prop and forward motion of the boat helps to both muffle the noise and pull the exhaust out.
The rear port on the riser serves only to supply cooling water to that area...it doesn't mix via the rear port. So yes, that port dead ends but it prevents a hot spot.
The reason to block off the flow from the manifold to the riser is dependent on the type of cooling system. If the engine is completely raw water cooled, no ports are blocked and raw water flows throughout the engine, into the manifolds, up the riser and out the thru the drive.
In a closed cooling system, the engine is cooled with regular automotive anti-freeze. The raw water flows into a heat exchanger (which acts like the radiator on your car) and out thru just the riser only. A stainless steel or composite block-off gasket is used in place of the one with open holes for the ports. Antifreeze is in the engine and manifolds. Sometimes the manifolds are not included in the anti-freeze system and are raw water cooled. That is known as a half or partially closed cooling system.
For trailered boats, a raw water system is best since it is simpler and easily flushed with fresh water. On boats that sit at the dock most of the time, closed or semi closed is better since the block isn't lounging about with raw ocean (bay lake river) water sitting in it. However these systems need a separate seawater pump and more hoses.
Manifolds and risers are maintenance items and need replacing. As long as you have it apart, install the new.
 
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Excellent information, thank you for taking the time. I see my pictures didn't upload. I ended up putting the original risers back on prior to readin this. But think I'm going to put the new ones on since I already have the extra gaskets anyways and am conserned with heat. I know this could be a million different thing potentially but I'm suspicious of the old risers now. Running the boat on earmuffs for no more then a few ministers at a time I noticed the engine got pretty hot pretty quick.

maybe I don't have the water cranked high enough? It's definitely cycling water but maybe not enough?

Any ideas?
 
Could be your muffs. I had to use a rectangular shaped muff (vs. round) on mine--wasn't putting enough water in with the hose. And turn the water on FULL blast.

Jeff
 
Example only. This is a rear exit manifold.
 

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I ended up installing the old elbows because I'm lazy. After a min of running my manifolds were HOT. Don't know if this is related to the risers or not enough water from running on muffs. I posted a thread on this topic with a video of the boat running, fans kind of in the way but what do you guys think?

https://youtu.be/1EqgEeMmxCE
 
raw water or "fresh water" cooled... if raw water, the gaskets between the manifold and the elbows should be of the passthru type.
 
sandkicker said:
raw water or "fresh water" cooled... if raw water, the gaskets between the manifold and the elbows should be of the passthru type.
Click to expand...

The boat, a 1978 searay is raw water cooled to my knowledge this means water straight from whatever body of water the boats running on. When I pulled the exhaust apart it had block off plates between the two gaskets where the elbow meets the manifold. So I replaced them when I reassembled. Should these not be there!? The new Barr elbows came with a single gaskets for each side that are open for water to flow through the passages and no block off plate..

confused!
 
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o2batsea said:
The Barr risers are made a little different. The Mercruiser ones are fully cast, but the Barr ones have the mixing tube press fit into the casting. If you look at the Mercruiser one you see some convolutions in the outside of the exit tube which helps atomize the water as it comes out. The Barr one has a slight flare to the exhaust tube which does the same thing to the water...just breaks it up. The cooling water goes up the front of the riser to an opening where it exits just before the engine exhaust. The water and exhaust mix in the Y pipe and exit thru the hub of the prop. The vortex action of the prop and forward motion of the boat helps to both muffle the noise and pull the exhaust out.
The rear port on the riser serves only to supply cooling water to that area...it doesn't mix via the rear port. So yes, that port dead ends but it prevents a hot spot.
The reason to block off the flow from the manifold to the riser is dependent on the type of cooling system. If the engine is completely raw water cooled, no ports are blocked and raw water flows throughout the engine, into the manifolds, up the riser and out the thru the drive.
In a closed cooling system, the engine is cooled with regular automotive anti-freeze. The raw water flows into a heat exchanger (which acts like the radiator on your car) and out thru just the riser only. A stainless steel or composite block-off gasket is used in place of the one with open holes for the ports. Antifreeze is in the engine and manifolds. Sometimes the manifolds are not included in the anti-freeze system and are raw water cooled. That is known as a half or partially closed cooling system.
For trailered boats, a raw water system is best since it is simpler and easily flushed with fresh water. On boats that sit at the dock most of the time, closed or semi closed is better since the block isn't lounging about with raw ocean (bay lake river) water sitting in it. However these systems need a separate seawater pump and more hoses.
Manifolds and risers are maintenance items and need replacing. As long as you have it apart, install the new.
Click to expand...

If I understand correctly.. The boat is raw water cooled, sothere is no reason for me to be running block off plates? If this is true and block off plates are ran between the elbow and manifold on a raw water cooled boat what kind of problems would that cause?
 
Well.... if raw water cooled ( and this means no heat exchanger, NOT that the engine gets its cooling water from what it floats in!) water has to get into the exhaust manifold, cool the manifold... and exit through the elbow. TYPICALLY this is done by water flowing from the top of a centerrise manifold (or the end of a log style) thru the juncture of the manifold and the elbow on passages that surround the exhaust port itself. Regardless of fresh (and its variants) or raw water, water must go in and out of the manifold on separate paths. Soooo.... if you are raw water cooled as you say ( NO HEAT EXCHANGER) how does hot water get out of the manifolds if you have blocking plates?????
 
sandkicker said:
Well.... if raw water cooled ( and this means no heat exchanger, NOT that the engine gets its cooling water from what it floats in!) water has to get into the exhaust manifold, cool the manifold... and exit through the elbow. TYPICALLY this is done by water flowing from the top of a centerrise manifold (or the end of a log style) thru the juncture of the manifold and the elbow on passages that surround the exhaust port itself. Regardless of fresh (and its variants) or raw water, water must go in and out of the manifold on separate paths. Soooo.... if you are raw water cooled as you say ( NO HEAT EXCHANGER) how does hot water get out of the manifolds if you have blocking plates?????
Click to expand...

it can't so it just keeps building heat... why on earth would someone put those in there then?! Looked at one picture on the internet and said " I got this, hold my beer" ? the guy that sold me this boat is such a ass.

I got the new elbows on (since I had them already) and used a single open basket in each side. No block offs Hooking up hoses and starting her up! I'll report back!
 
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Got those block off plates out went to test things and my starter died on me lol. One new starter and she's running. STILL OVER HEATING! I'm going to put it in the lake today and see what happens. It's either not getting enough water on the hose or there is a restriction somehwere. Really thought those plates were the problem ����
 
........................

sandkicker said:
Well.... if raw water cooled ( and this means no heat exchanger, NOT that the engine gets its cooling water from what it floats in!) water has to get into the exhaust manifold, cool the manifold... and exit through the elbow. TYPICALLY this is done by water flowing from the top of a centerrise manifold (or the end of a log style) thru the juncture of the manifold and the elbow on passages that surround the exhaust port itself.
Bob, no offense..... I just want to add some info for the OP here.

These ports that surround the main exhaust port are the "seawater transfer ports".
They can easily become restricted with rust scale.
Once restricted, over-heating is imminent.



These seawater transfer ports can often be cleaned/cleared out.
In some cases, the surfaces will require dressing up via a Machine Shop surface sanding machine.
In either event, this will bring new life the Manifolds and Elbows.
Same with Spacers/Risers if so equipped.
Regardless of fresh (and its variants) or raw water, water must go in and out of the manifold on separate paths. Soooo.... if you are raw water cooled as you say ( NO HEAT EXCHANGER) how does hot water get out of the manifolds if you have blocking plates?????
Good question!
The only answer is...... the manifolds are fitted with a seawater Inlet and and a seawater Outlet.
The SS Block-Off Plate (with the weep hole) prevents full flow via the "seawater transfer ports" (from manifold up to/through Elbow).
The Elbow then must be fed separately, and above the SS Plate.
Otherwise, the SS Block-Off Plates should NOT be used.
Click to expand...
 
Bt Doctur said:
post a pic of the therm housing and the hoses.Has the impeller in the drive been replaced?
Click to expand...

I will. The drive and impeller has been rebuilt. The impeller basically blew up so there could be pieces in there dealing havoc. The manifolds are the log style ones with brand new BARR elbows I opened both ends of the manifolds and cleaned em out pretty good, pass through type gaskets no block off plates in this raw water boat any longer. We are about to put it in the lake to see what happens. On the ears there is deffanitly not enough water coming out of the boat in the hose. Maybe it's the water pressure at the house on the hose?

the guy had one of the thermostat hoses routed wrong I posted picture in here and was told how to make the correction. That being said I think the hoses are all routed correctly but I'll still try and post a picture when I can

manifolds should be no more then 150-170* with sufficient water flow correct?
 
..."The impeller basically blew up so there could be pieces in there dealing havoc."

Uh-oh! Had that happen to mine and she cooked herself until I found the missing vanes.

Jeff
 
Well yesterday was a success, the boat ran great and she ran cool. I need to get a IR thermometer so I can actually get a real temp read off the manifolds. Althought they still seemed a bit hot, they were nowhere near what they were on the hose and they seemed to level off at a consistent temperature.

My questions, is it safe to assume the hot manifolds and overheat issue is related to being on the hose? Or could there still be a threat of restriction and if so where?
How directly would higher manifold temps effect the temp gauge on the dash?
Should I still consider replacing my manifolds?

The temp gauge on the dash hardly moved especially while cruising. Only time it would creep up about 1/2 way is when I would cut the engine, obviously stoping the flow of water causeing a spike in temp. Other then that, running no more then 1/4 on the temp gauge all day.

Got up to 30mph and it felt great! Wouldn't have gotten this far without you guys. I'm sure this boat will continue to be a project but just getting it on the water and actually having a good time was something I was beginning to doubt I would ever get. So I just wanted to say thank you to ALL of you. If any of you are in/ ever in Ventura CA let me know, I owe you a beer!
 
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Glad to hear it. Like I posted above, I HAD to go with square ended muffs to get enough water to flow. The common round ended muffs didn't shoot enough water in.

Jeff
 
fastjeff said:
Glad to hear it. Like I posted above, I HAD to go with square ended muffs to get enough water to flow. The common round ended muffs didn't shoot enough water in.

Jeff
Click to expand...

those are the ones I have.. well more of a rectangle then an square. Either way we are in the water but the whole things a mystery
 
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