Looking to remove Corsa side exit, thru-hull exhaust, and run through outdrive (normal) on 2016 280SLX...

[NicolasB]

I am not the 1st owner of the boat, have had it for 4 years and the boat is great, but the side exit Corsa exhaust makes some noise (not a whole lot) even when it is switched off. I just want the boat as silent as possible, the exhaust is for fun and doesn't add any performance/top speed. Is there a way I can buy some stock exhaust system parts to swap out and then maybe sell the Corsa parts? I just want a pipe that goes from the header manifolds down to the outdrive area. I can deal with capping off the side exhaust ports to keep water out. I am attaching photos in hopes that someone will be able to give me some input. My local mechanic didn't think it was going to be an easy thing, but I (being a former car mechanic) think putting in stock pieces shouldn't be all that difficult.

Thank you!

 

[Ididntdoit]

looks like its hooked up that way now......there should be a switch for "captains choice" exhaust or something like that

 

[NicolasB]

looks like its hooked up that way now......there should be a switch for "captains choice" exhaust or something like that

Oh yes, there is a switch and I keep it closed to 99% of the time. However, even when it is in the closed position, there is some exhaust that leaks past the metal flaps inside and the exhaust still kind of burbles out both sides of the boat through the ports. Like I said, it's not that loud, but I would prefer it to be silent. You can hear it especially when you pull in up against the dock and the sound echoes off of it. I was hoping there would just be a factory exhaust pipe that I could swap out in place of these Corsa pipes.

 

[Ididntdoit]

There is a mercruiser y pipe that most boats come with......but you'll need to pull the motor to do it - I would check to make sure the corsa valves are completely closing/sealing - sometimes the get stuck....

 

[NicolasB]

There is a mercruiser y pipe that most boats come with......but you'll need to pull the motor to do it - I would check to make sure the corsa valves are completely closing/sealing - sometimes the get stuck....

Yes, I verified they were shutting. I manually operated the little actuator arm, just isn't an airtight seal, which I understand is a difficult thing for a 4" exhaust. There is a pipe down below (seen in photo) that should probably stay (maybe?) and then I just need a connecting pipe from the exhaust manifold outlet to go to that pipe. Or perhaps it is a much different setup, and the engine would need pulling...hmm. Anyone have photos of their similar engine with regular exhaust?

Thank you

 

[NicolasB]

Could I get a pipe custom made that connects from these 2 points (circled in photo) and go that route? This would just bypass the side outlets (eliminate them) and just shoot it out the outdrive. Is there anything that needs taking into consideration otherwise? Any water that flows through them for cooling or anything?

 

[NicolasB]

https://www.amazon.com/Mercury-Mercruiser-Quicksilver-879288A14-Kit-Intermd/dp/B00N9HJHSC

Something like this, but I think the end toward the outdrive needs to be round instead of oblong, like this one is.

 

[Bill Curtis]

https://www.amazon.com/Mercury-Mercruiser-Quicksilver-879288A14-Kit-Intermd/dp/B00N9HJHSC

Something like this, but I think the end toward the outdrive needs to be round instead of oblong, like this one is.

Interesting. Those sure look like they would fit, but I would compare / verify in the mercruiser parts lookup for stock exhaust for that engine.

If they are correct, your conversion will be very easy (aside from the fiberglass work to plug the holes in the fiberglass that remained after the exhaust removal.).

IMHO: Maybe it's just me, but love the sound of a big block with thru hulls. Wife has a different view, but the captains call would possibly be a middle ground.

 

[NicolasB]

The boat does sound good with it opened up, but it's a cruiser that tops out at 46mph, so it doesn't feel very genuine having a boat that sounds like a racer, but is actually slow.

I would probably leave the ports in the fiberglass and just make caps inside.

Does anyone have a link for a parts diagram for these engines?

 

[paulswagelock]

Here is the exhaust for an 8.2 non ec.

 

[NicolasB]

That is excellent thank you

I am thinking the only issue is that the mercruiser elbow pipe is oval on the outward end, and mine looks to have a round pipe, maybe not? I will have to open it up this evening and take a closer look and see if I could still make it work, perhaps with an oval-to-round adapter of some kind.

 

[Lazy Daze]

Yup, you can do what you're talking about. The Merc exhaust manifold is stock and you will have the stock Y-pipe down below. Everything in the middle can go away and you can go back to stock.

Once you get past the exhaust manifold (which carries exhaust gas and water via a "pipe within a pipe"), everything is an open pipe.

The rubber boots that connect things are flexible.

 

[NicolasB]

Yup, you can do what you're talking about. The Merc exhaust manifold is stock and you will have the stock Y-pipe down below. Everything in the middle can go away and you can go back to stock.

Once you get past the exhaust manifold (which carries exhaust gas and water via a "pipe within a pipe"), everything is an open pipe.

The rubber boots that connect things are flexible.

Yes! I opened it up and looked more closely tonight and I do have the stock lower manifold! I will order these Mercruiser elbows and it will actually be a very simple change. Very excited this will be straight forward. My only question, there is a small black hose that connects off the side of the block through a brass fitting (smaller one in pic) and goes into the Corsa pipes. I am thinking it is water to keep the on/off butterfly valve cool? I would guess that hose can just be blocked off. Pics attached:

Also, here's a pic of where it attaches to the lower manifold:

 

[NicolasB]

44267A02​

I looked up that part number, and the elbow does not look correct. It only has 1 bend in it, where the one I require would have to have 2 bends. The elbow I found on Amazon looks to be just the right shape, seen here:

I have to verify the part numbers, but the 44267A02 doesn't seem to be the one for my engine.

 

[NicolasB]

https://www.mercruiserparts.com/8m0095834-elbow-kit

This seems to be it. The one previously found in the parts diagram up above is for a "non-ec" engine, which means not emission controlled. This one is for emissions controlled, meaning the exhaust manifolds have catalytic converters built-in.

 

[NicolasB]

Final question:

This pipe comes with a 2", 4" or 6" riser, and I don't know which one I would need. Any way I can verify this part of the equation?

(PS - Sorry for so many posts this evening, I normally do not have any caffeine, but I had a little bit early today and it still has me wired!)

 

[paulswagelock]

Riser height is determined by the float level that the engine sits in the water to keep water from flowing back through the exhaust. Too high is ok if you have clearance, too low is bad….

 

[NicolasB]

Riser height is determined by the float level that the engine sits in the water to keep water from flowing back through the exhaust. Too high is ok if you have clearance, too low is bad….

So what exactly is the riser? I figured it meant the pipes were different lengths, is it something else?

 

[Lazy Daze]

Small hose... remove the bronze elbow and replace it with a bronze pipe plug.

A riser will raise the exhaust elbow in a system where there is a separate elbow and riser. You don't have that - nor do you need to mess with changing the height of your elbow since that's already set. You just need the correct length down pipe between the exhaust elbow and y-pipe - or modify the existing SS pipe work.

 

[Bill Curtis]

So what exactly is the riser? I figured it meant the pipes were different lengths, is it something else?

Riser is basically a spacer between the manifold and elbow that bolts on top of it. The height is determined by where the exhaust elbow is in relationship to the water line at rest.