Exhaust questions for a 280 AQ-gctid394788

[SKUA_28_Contessa]

Why aren't the manifolds plumbed to flow cooling from both ends at the same time?? Why is there a plug in the risers, that isn't used?? Anybody try plumbing a T and cooling from both Ends?? This is the raw water exhaust only system.

Aside fromt the generic OEM style replacement manifolds, and the uber expensive SS ones, anybody have any thing different?

[2850Bounty]

Skua wrote:
1.... Why aren't the manifolds plumbed to flow cooling from both ends at the same time??

2.... Why is there a plug in the risers, that isn't used??

Anybody try plumbing a T and cooling from both Ends?? This is the raw water exhaust only system.

Aside fromt the generic OEM style replacement manifolds, and the uber expensive SS ones, anybody have any thing different?

I'm not aware of an AQ280.... you must be refering to an AQ260.

1.... I'm also not aware of any AQ260 manifolds being supplied sea water from both ends simultaneously.

2.... The AQ series OEM V/P exhaust risers are not fitted for direct port cooling water, so you must be looking at the BB engines, or perhaps the 3" Universal Barr, or the HGE, or another brand manifold and riser combination.

If you want an OEM replacement riser that offers a port, look at the HGE products. I seem to recall a riser that is ported.



The OEM manifolds work well when the spent sea water enters from one end, and is then allowed to use the transfer ports between the manifold and riser.

What modification are you wanting to make, or what problem are you having?

.

[SKUA_28_Contessa]

The engine is 260A anf the drive is a 280. Currently have barr risers and manifolds which are almost plugged up athe rear cylinders, and the bottoms of the riser outflows. I noticed that there is a plugged port under the risers, and the manifolds have the in port on the fronts and plugs on the back. Why not front and back like some Mercs and Crusaders do? I know that some of these feed oil coolers and the like. I would think that feeding water front and rear of the manifolds would decrease the plugging of the rear cooling jackets.

[2850Bounty]

If you have an AQ 260, you'll also have the 95mm OD Y-pipe.

This Y-pipe requires the OEM style exhaust manifolds and 95mm outlet risers.

These risers are not ported for a sea water fitting.

If you have the Barr universal exhaust manifolds (that are ported in the risers), these will be a 3" riser outlet.

If so, you must have an adapter of some sort to take the 3" to the 95mm.

But back to your question re; feeding each end of the manifold:

In order to do this, you'll need to block off the transfer ports between the manifolds and risers with gaskets and a SS block off plate.

You'd then feed the manifolds from the front, exit from the rear, then route this up and into the riser port.

To my knowledge, this cannot be done with the OEM AQ260 exhaust, unless you go with the HGE style OEM replacements w/ 95mm risers that are ported.

Can you post a few photos of your exhaust?

,

[Guest]

There may be aluminum after market support. I never looked. When mine die I'm going stainless, but i'll make 'em. I realize I'm not normal (In many ways!!).

You think that by using both that the flow would stop the crud from building up? I think it would just build up at the riser to manifold connection like it always does. It's the 'weak spot' in the system. You could go in the front of the manifold, out the back and into the riser to bypass the manifold to riser gasket joint holes...but on my boat there is not a lot of space to add 90 deg fittings etc that you would need (Unless you went crossflow from one bank to the other)!!! Anyway, with an open type gasket that would just make a parallel route for the water to flow.

Sounds like a lot of complexity for a really simple system. I like a minimum of connections with a system that can pump your engine room full of water (Don't ask me how I know!)

Why not just clean out the passages? There are lots of ways, manual wire brush, muriatic acid etc. As long as there is a good mating surface for gaskets where the riser meets the manifold you're fine. If not you can touch them up with a file. Yu just need a minimum thickness for sealing (Some say 1/4 inch, I like a little more!).

The plugs in the riser are for full closed cooling systems. The manifolds themselves are cooled with antifreeze, then the raw water is dumped into the risers to exit the system. Volvo never had this setup stock (so I've heard, I'm no expert), but it's by far the best way to go. I have it on my Mercruiser and the manifolds last forever. It seems to require a larger heat exchanger than the 1/2 system (engine but not manifolds) though.

Chay

[2850Bounty]

Again, the OEM AQ260 risers are not ported/threaded for a sea water supply.

Nor was the AQ series V-8 able to be fitted with a Full closed cooling system.

In order to do this, you'd have to be creative and use the HGE style OEM replacements that are ported.

With the standard AQ260/225 exhaust, the manifolds are ambidextrous, meaning that each is ported at either end.

The AFT end port then becomes your drain point for winterizing.

When the AFT plug is removed, we must probe the port for rust scale debris.

If not probed, perhaps this is why the manifold is becoming filled with scale here.

[SKUA_28_Contessa]

Well I had noticed that the temp was running higher than normal particularly at idle. So I figured plumbing from both ends would help a tad. However after removal of the manifold and riser on the port side, it was clear they were munged up a bit. The bottom portion of the riser swirl was plugged with rust flakes, and the manifold was plugged with sand and rust underneath the middle 2 ports, and the back port was clogged with sand. I ran a coat hanger through them and got a crap load of debris out, but I have decided to replace them as they are of unknown vintage.

[2850Bounty]

In reading your first post, I'm curious as to which manifolds are on there now.

Can you post photos of them and your engine for us?

.

[SKUA_28_Contessa]

Sorry no photos boat is 60 miles away. Its a standard 260A, and the manifolds and risers are Barr. I have a 90 elbo on the front of each manifold,and a plug on the rear. There is a cast iron plug in the bottom of the risers, under the bend between the riser and the manifold. I wanted to run an elbo to each end of the manifold, and let it continue to flow out the risers in a normal fashion

[2850Bounty]

I'm all for modifying things if it becomes necessary.

However, if the transfer ports are clean, and when the sea water flow is good, and when the OEM rubber couplers aren't burried into the riser scallops, we just don't run into problems with the OEM manifold configuration on these engines.

Are you using the OEM rubber exhaust couplers?

If so, where are the aft-most riser band clamps squeezing down on the couplers?

These couplers are always..... repeat ALWAYS too short, and the aft-most "riser" band clamp eventually squeezes the rubber material into the scalloped areas.

These scalloped areas MUST remain open and free!

(see scallops here)



When this does occur, the outgoing spent sea water is greatly restricted.

Then we chase our tails thinking that the problem is somewhere else!

The cure is to purchase new 95mm exhaust hose that is approx 3" longer than the OEM couplers.

Now the band clamps can be placed further up the riser outlet, away from the scallops.

This is not a new issue.... it's been around for quite some time, but it may take several years to show up.

Why Volvo Penta, Sierra and others continue to sell these that are far too short, is beyond me! rod

.

[Guest]

Perhaps rather than try to re-plumb the OEM system to something custom, just drain/flush more often? The OEM raw water system on an AQ series V8 is pretty easy to drain or flush out the manifolds. How often has this been done in the past? At a minimum, it would be done during winterization (assuming you live somewhere that you need to winterize). By flushing, I mean more than simply pulling the drain plugs off the backside of the manifolds and letting gravity do all the work. You need to probe the drain holes, and the longer the piece of metal, the better. I use a thin piece of stainless metal, as stolen from an old wiper blade. A standard wiper blade of any kind has 2 thin strips of stainless that keep the rubber blade itself in a nice straight line.

For a bit of a "power flush" (and not just gravity drain), you can easily disconnect the rubber inlet hose feeding each manifold and stick a garden hose in the rubber inlet hose. Disconnect the rubber hose at the t-stat housing and stick the garden hose nozzle in that end. I just use a basic garden hose sprayer nozzle, and I can usually just jam the tip of the nozzle into the rubber hose so that it will stay in place by itself even with the garden hose flowing at max. I have also stuck the garden hose nozzle in the drain holes on the manifolds too, as this can loosen up additional junk due to the water flowing in the reverse direction. In cases where things are really clogged (but still re-usable), I take the manifolds/risers off completely and flush/probe from all points available until clean.

[SKUA_28_Contessa]

Clamps were on the edges of the non oem couplers. No evidence of extrusion into the port area. New parts ordered from Partman.com. They're close, good service, and reasonable price. I'm thinking maybe I'll plumb in a fresh water flush into the impeller intake.