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I have a 2015 V-275 with a Volvo 320 r.w.c. running in brackish water. This up coming season will be my fifth season on the boat. I have approximately 100 hours on it now. The engine has catalitic convertors. This is new territory to me with the cats. Have any members had to deal with the manifold and riser replacement on these engines. I am aware that the manifolds, elbows and cats run around 6K plus labor. I am trying to find out from others the life expectancy of this set up and weather or not the cats have to be changed out with the manifolds and elbows. Any information from experience would be appreciated. Last season she ran fine, I am just looking ahead for maintenance issues.

Hello Byron, I've ran big and small block chevys rwc on boats used for shrimping, the manifolds and risers would give 5 yrs with no problem, with running hot/dry is when they seemed to self destruck. We don't use cats down here so can't help there but the most common problem is the elbows clogging with rust/scale in the water discharge slots, we would run a wire/coat hanger in them at the start of the season just to be sure, if your running a little warm then normal sometimes the restriction of discharge water is the cause. Manifolds and risers are under a grand for a set and really not hard to replace so I don't know about the 6 grand. As said I haven't seen marine inboards with cats, but I would bypass/remove them if they were just for exhaust emissions. Good Luck, John

Thanks for the info averep. Like I said these cats are new to me too. My last two boats were both 5.7 without cats and were good for five years with out any issues. All inboard recreational inboards manufactured after 2009 will have the cats. Its the law. The problem is that they are built into the exhaust system and located between the manifolds and the elbows. They save sensors on both sides of them which go through the ecm. With the electronics involved in these newer e.f.i. engines ,if I were to eliminate them some how, i,m quite sure there would be problems. Maby someone out there knows of this is true. By the way. I looked them up and the cost of two manifolds, two elbows and two cats is around $6,000.00 plus tax and installation. These manifolds are big as to be able to cool off the cats. Even if you have a f.w.c. engine with cats the manifolds are raw water cooled as they need the volume to cool them off. To make a long story short, if you are considering buying a late model twin gas engine boat, figure on spending around 16-18k every five years on manifolds and risers. Until they figure out a way to put cats on outboards, I guess we will be seeing more of them.

That's new to me, since Katrina we run Cummins now, but if their wired in maybe just unplug and see what happens. With all these people that are reprograming their computers for the cars it seem like someone would have a bypass program already done and available for this app. I know of guys down here that get in to the outboard computers to change factory settings to improve performance .Manifolds and elbows can be purchased with risers, offsets , etc. to redo any system and if possible to bypass an get the system to work. Just seems like somebody tried this already before giving up that much cash. John

You know averep, this is why I love these forums. There are always ideas out there. When I get the boat back in the water why not just unplug those sensors and see what happens. Until that time I will keep on asking around different forums and try to find any other options before I have to change out the units. I know I have another good season on what I am running. Thank you for your input.