View Full Version : Need exhaust help!!!!

12-17-2012, 10:43 AM
The deck is off the TR and this is the first time I've tried to fit the exhaust together........
As is clearly visible, there's a problem w/the Q&Q down pipe and the Y-pipe.
The Q&Q is off of a Blackhawk Donzi boat (502), the Y-pipe is from a 496 (supposedly).
Is there more than one Y-pipe?
Can anyone help?

12-17-2012, 11:43 AM
your problem is the manifold is not a center riser, the outlet is actually rearward of center, you need an aluminum center outlet manifold

I know, I know, more moolah $$

12-17-2012, 11:54 AM

I would swap the manifolds from side to side and turn the risers around 180 degrees. This should give you the extra couple of inches you need to align the Q&Q and the Y pipe. :D

See what happens and go from there.


PS, or what Jim said. :bonk:

12-17-2012, 12:03 PM
George the real problem is the manifolds are the wrong color...:biggrin::biggrin:

12-17-2012, 12:25 PM

Meant to ask.... Of this setup, what is original and what is not?


12-17-2012, 01:06 PM
[ QUOTE=$originalposter]I would swap the manifolds from side to side and turn the risers around 180 degrees. This should give you the extra couple of inches you need to align the Q&Q and the Y pipe. [/QUOTE]

Bob's suggestion will put the manifolds in their proper spots. The Gil style manifolds were designed to have the off-center part to be more forward vs. more back like you have them bolted on. I think by swapping them to their proper sides it will hopefully work itself out.

12-17-2012, 01:35 PM

Meant to ask.... Of this setup, what is original and what is not?


Bob, the manifolds came w/the boat.
The original risers/tails were dry to the transom.
So, I bought the risers, which are called Magnum Choice and intended for Q&Q.
I bought the Q&Q from someone here on this site.

12-17-2012, 01:58 PM
What Bob said. If not a pair of differet risers like Merc SS but I think Bob is on the $$.

12-18-2012, 11:41 AM
George, I have a 496 and a 502 Y-pipe. I did a rough measurement and they seem to be identical. The 502 pipe was buried behind my workbench, so I it was tough to be accurate, but I'll try and remember to pull it out tonight and get more accurate measurements.

12-18-2012, 01:56 PM
I am thinking along the lines of what Tilbert said, something else popped into my thoughts. Is the cam you are using any more radical than the Magnum cam, they look a little short which may cause reversion issues.

12-18-2012, 04:48 PM
No Phil, nothing radical, I picked the cam to work w/this setup.

OK, just as I thought, the manifolds are symmetrical. I thought they were, but I wasn't going to say anything until I tried swapping them. So a picture as it is now, looks just like the picture above.

A couple of things, The Gil setup like this was designed for their Silent Choice diverters. They are significantly different from the Corsa Q&Q that I have. It seems to have a dogleg to correct for the problem geometry. I didn't take this picture, so don't blame me for the for the fuzziness.

12-18-2012, 04:52 PM
But here's another possible solution;
Below is a picture of another Gil Magnum Choice manifold and riser currently for sale on eBay.
You can see in the picture, there's a wedge between the manifold and riser flanges.
These wedges are available to give some flexibility of adjustment.

12-18-2012, 05:06 PM
By only adding a wedge, the tail of the diverter ends up below the inlet to the muffler which isn't in itself, a good solution.
But you can get the down tail to line up w/the Y-pipe.

So, imagine a spacer AND a wedge between the flanges so that all the pipes line up.
The spacer would have to be about 5/8" thick, and a wedge like in the picture above on top.

Money has always been such an issue w/this project. I really need to figure this out, or just hose the riser to the mufflers.
As many of you know, gil has gone out of business. Hardin bought the remnants and rights, but they don't seem to be making these diverters, nor are there currently any for sale. Not that I could afford any if they were.

Any comments

12-18-2012, 07:08 PM
I have a simple solution if you know someone with a tig welder. Carefully cut the downpipe and reclock and weld it to line up with the y-pipe. Thats if you dont find another solution. Thats also assuming the valve is on a vertical axis behind the downpipe as it appears.

12-19-2012, 08:59 AM
I don't know if it's the angle or what but your manifolds look like the stock Gil / Merc ones, just like the ebay picture you posted. Those manifolds don't look symmetrical by any stretch.

Hardin makes replacements now and this is how they should look when the manifold and tail are bolted together


As you can see, the end of the standard tail ends before the end of the manifold Vs. your pic and the ebay pic where the tail ends after the manifold because they are bolted pointing off the short side Vs. the long side.

12-19-2012, 11:43 AM
Have you tried turning the manifolds around yet as Bob said?

12-19-2012, 11:51 AM
George you say they are symmetrical but the photo shows differently, in fact the photos posted by others show the same thing.

12-19-2012, 12:48 PM
Are you sure you didn't put them back the way you hd them before? :tongue: You have been under alot of stress lately. :D

12-19-2012, 01:00 PM
The manifolds should look like the pic Vette showed. You just move the water plug from front to rear and turn the risers 180, should line up on the other side of the engine.

12-19-2012, 01:45 PM
Sorry guys, but the two manifolds are identical.
When I switched them, and I did switch them, the configuration was identical.
I'm looking at other solutions.

12-19-2012, 03:27 PM
That does not make sense unless you have 2 of the same manifolds but at least then one should line up and not the other...is that the case? What about a ceneter riser like a stock mercruiser or Merc SS. Somebody you know must have one laying around to line up with. If not I can mail you one.

12-19-2012, 04:12 PM
George, you lost me here... your pic clearly shows a rear off set on both manifolds, if you reverse them then the offset goes to the front on each side...

what are we missing here?

12-19-2012, 05:16 PM
The manifolds are identical from the molds for the offset of the heads on the block. So the riser position is equal to the transom. Same way big block chevy heads can be switched from side to side. No designated sides.

12-19-2012, 05:39 PM
Yes Jim, the two manifolds are identical. The are not marked port, starboard, left right, or anything.
The way it works, and it's very clear if viewed from overhead (but I didn't take a picture, and I won't be able to take one until tomorrow afternoon), the offset is to adjust for the cylinder bank offset, and the center line of the outlet is just aft of the center of the engine, on both banks. In other words, the two outlets line up, but they are about two inches aft of the center.
If they (the manifolds) were designed to exit at the center, there would have been less offset.
My problem (apparently) is I'm trying to use a diverter intended for a manifold w/a center exit.

So, at the moment, I'm considering using some Y-pipe caps that are offered by Hardin so I can leave the Y-pipe in place, and run hose from the risers to the mufflers. At least until I can find and afford the proper diverters. W/the Y-pipe left in place, it'll be easy to add the proper diverters.

Below is a picture of two of the manifolds........

12-20-2012, 09:57 AM
Standard plumbing caps work fine for about 1/3 the price, been on mine for a few years now.

I still think you are missing the boat on switching sides, it will move the risers forward!!!!! IMO they are on the wrong sides!!!!

12-20-2012, 11:26 AM
You tried this George? -didn't work did it...


12-20-2012, 11:39 AM

The offset on the manifolds is equal to the offset on the cylinders, so it won't matter what side they are on, the back of the riser will still be at the same distance from the transom. Hope this help clear it up.


12-20-2012, 01:20 PM
JayZ's #1 picture shows the riser tip ending up even with the end of the manifold when it is on the correct side! The way George has his mounted the riser tip is well past the rear exhaust port, mounted the other direction the tip is nearly even with the rear exhaust port
The shot of the set with the wedges are also backwards but worked for that guys application. Going to be some egg on face action!

12-20-2012, 01:30 PM
When you put the manifold on the other side, the offset will move forward but the manifold will bolt further toward the rear an equal distance. So, it won't matter. You still end up with the same problem. The photo shows the 1357 side, the 2468 side manifold will bolt futher back on the block negating the distance that was gained.

Is that any clearer?


12-20-2012, 02:08 PM
Phil, I did change them side to side, just like I posted.
And just to be sure, I removed one manifold and set it in the bilge.
Next, I removed the other manifold and placed on the side opposite.
They are identical, and it matters not which side they are installed on.
Here's a picture from overhead that shows them to pretty good advantage.
You can easily see the cylinder bank offset, and how the manifold outlet
centers line up just aft of the center line of the carb.

12-20-2012, 02:26 PM
So, since these diverters (Corsa Q&Q) don't fit my manifolds and risers (keeping in mind that manifolds cost more than diverters), I'm going to offer these for sale. They are essentially like new w/3" down tails. I paid $600 for them, I don't think I'd expect to get that much for them, so if anyone is interested, make an offer.

12-21-2012, 08:06 PM
So, here's the actual diverter that will work w/ the manifolds I have.
W/the dog leg in the down pipe, there is good geometry and room to
position properly w/o any jamming:

12-21-2012, 09:02 PM
I had Corsa bend up some custom diverters for my boat last winter. I needed a dogleg on the thru-hull side of the pipe to bring the exhaust tighter in towards the drive to clear the transom cutout. Took a lot of measurements and inside/outside pictures and sent them in to Corsa, about a 10 day turn which isn't bad at all.

They do nice work... I think retail on the custom diverters and installation kit (wiring, breakers, etc) was around $1600. My buddy is a dealer so I ended up getting them for cost plus a case of beer (and he even shared the beer while we installed the diverters).

12-21-2012, 10:36 PM
Not that it matters anymore George, but I did measure up the two y-pipes. The 496 and 502 y-pipes are the same.