New exhaust manifold advice

[zaayer]

I have a 2012 Volvo Penta 8.1 GiC-Q 400HP catalyzed engine. My manifolds are coming to the end of their life. The parts for the manifolds alone is over $4000 per side. That doesn't account for the elbow or anything else on exaust side. The manifolds are impossible to find so I am looking for a substitute. Does anyone have any advice on a replacement maniford that may not be catalyzed? I know the computer will look for the O2 sensors, but I believe there are devices to convince the computer that the nonexistent O2 sensors are running correctly. I am also willing to do aftermarket stainless exaust if that makes more sense. I just don't know where to start. Any advice would be much appreciated.
https://www.volvopenta.com/shop/0/part-sections/54160227 is what my exhaust systems looks like.

 

[Scott Danforth]

Contact Raylar engineering as they are the 8.1 experts

Your ECM will need to be reprogrammed to go non-cat


There is a set of VP manifolds on ebay

*OEM* Volvo Penta Port & STBD V8 Exhaust Manifold | eBay

Good Condition, Ready To Install.

www.ebay.com

 

[zaayer]

Contact Raylar engineering as they are the 8.1 experts

Your ECM will need to be reprogrammed to go non-cat


There is a set of VP manifolds on ebay

*OEM* Volvo Penta Port & STBD V8 Exhaust Manifold | eBay

Good Condition, Ready To Install.

www.ebay.com

Those manifolds seem to be for a smaller V8 than the 8.1. The part numbers don't match up. Would you try to stick with the catalyzed exaust or would you try to change to non catalyzed? I am finding the manifold for sale, but out of stock. The price for the manifolds only is about $4300 per side. That is only the manifold. The elbows seem to run about $1400 per side. The cats will be about $1500 per side if they need replaced.
The one manifold seems to be weak near the O2 sensor. These are Aluminum so I am told welding probably won't work.

 

[cyclops222]

Aluminum can and is welded for repairs.

 

[Scott Danforth]

I personally would never have bought a cat motor. And if I was in your shoes, I would go with the full Raylar package and be pushing about 500hp

 

[Lou C]

Agreed on never buying a cat converter motor. A relative of mine had one, here in the salt pond and I convinced him to trade it before it had problems and buy an outboard powered version of the same boat. He'll be far happier with it.
For a simple comparison you can buy a complete exhaust for Volvo inboard gas engines from Barr Marine (good aftermarket) for approx $1000.
Cat engines in boats are plagued with check engine lights, fault codes and astronomical repair costs.
Now tell me EPA folks, just how much does this improve air quality? You don't know? and you have cost the consumer thousands for that? Let's go Lee Zeldin.

 

[cyclops222]

The high failure rate of EPA mandated parts does not enter into being less GREEN.

 

[zaayer]

I personally would never have bought a cat motor. And if I was in your shoes, I would go with the full Raylar package and be pushing about 500hp

I bought the boat used and had no idea what I was getting ont wth a cat engine. This boat has around 200 hours and runs great. I talked to Raylar and they sent me to Custom marine. I have sent them pictures of my exhaust system and I am hoping that they can help but I have not heard back. I am searching for what else to do.

 

[zaayer]

The only part that is currently showing a problem is my starboard manifold. The area around the O2 sensor is weak. I have found one on ebay, but it is used and pricy. I am debating on whether or not to order it. I don't know if the other exhaust parts are also going bad or if this paticular part is just poorly manufactured. Does anyone have any advice on what they would try? I did see a component that can trick the motor into thinking the O2 sensors are operating correctly. However I don't know if the O2 sensor before the cat gives info for the fuel/air mixture, or is ut just used to compare the exhaust before the cat and after to make sure the cats are working. I also have 4 temperature sensors on the two exhaust. Do I need to trick the computer into thinking the temps are fine of will it not care?
I have thought maybe I can get a computer for a 8.1 non cat Volvo and run normal exhaust with this. However I am not sure if that would work. My engine is not the Gi (375hp) or GXI (425hp). My engine is rated at 400hp. Does that mean that it is somehow different from the Gi or Gxi model other than the exhaust. Is my cam different? I have so many questions and don't know where to go for advice. My local boat shops are not much help.

 

[Bondo]

Does anyone have any advice on what they would try?

Ayuh,...... As noted above, aluminum is easily welded,.....

You did say the manifold in question is aluminum,....

 

[zaayer]

Ayuh,...... As noted above, aluminum is easily welded,.....

You did say the manifold in question is aluminum,....

I had a professional welder give it a try and he said that the impurities that have been absorbed into the casting were too much. He could hardly even get filler rod to adhere. I am told he is good, but I do not know that for a fact.

 

[Bondo]

Ayuh,..... I once welded up an old Harley block like that,.....
I ground it out a good bit, mig'ed in a puddle, ground it out again, mig'ed it some more, 'n did that several times,......
Each time I did it, I got a little more good weld, 'n a little less crap, 'n bubbles,...
After several times, I got a nice clean weld, n that Harley is still runnin' today,....
(while it still leaks oil, it don't leak where I fixed it,.... )