Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

[mercruiser-mitch]

Hi guys, Im sorry for asking this but I have had a look around online and can't find much info on this.

I am new to boating and my mate has a Mercruiser 3.0 alpha one TKS engine that is now out the water for maintanance.

Basically I am asking about performance exhaust for the 3.0 engine, I have seen many for the V6 and the V8 exhausts, but not for the inline 4 engines.

I am sorry if this is a novice question but does the exhaust need to have its output into the water? can a manifold and exhaust be fitting above the water line? Ie instead of going down and out, can it not go up and out above the engine? I am unsure of the noise regulations for marine engines, can anyone enlighten me?

Thank you for your help!

 

[gadget73]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

Yes, you can do what is called a through-hull exhaust. Not sure exactly what your manifold looks like, but on a typical V engine with a center riser, basically what is done is a large diameter exhaust pipe is run back at a slight downward angle and attached to a fitting that goes through the transom above the waterline. The stock through the outdrive exhaust is purely for noise reasons, which you may start to appreciate after a while. There is what is called the Captain's Choice system, which is basically a valve that switches from through-hull to outdrive if you want to kill the sound.

 

[mercruiser-mitch]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

Yes, you can do what is called a through-hull exhaust. Not sure exactly what your manifold looks like, but on a typical V engine with a center riser, basically what is done is a large diameter exhaust pipe is run back at a slight downward angle and attached to a fitting that goes through the transom above the waterline. The stock through the outdrive exhaust is purely for noise reasons, which you may start to appreciate after a while. There is what is called the Captain's Choice system, which is basically a valve that switches from through-hull to outdrive if you want to kill the sound.

Ah ok, the engine is an inline 4 engine and not a V engine, so I guess its less complicated lol on an NA engine, wouldn't a large bore exhaust harm the power due to the lack of backpressure and scavenging of the exhaust cylnders? Im more into automotive tuning than boats (at the moment lol)

The boat will be used for wakeboarding/fun so noise is good lol Would stainless steel be ok for the material? What kind of downward angle would be needed to ensure that the water wouldn't get in?

 

[mercruiser-mitch]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

The exhaust exits though the prop hub, would this be an issue if a custom exhaust removed the manifold and risers? Would there be anything that would need blocking off if I were to remove the exhaust? I have seen many photos of the whole exhaust system corroding in the saltwater, so I figure I might as well sort out the exhaust before it completly corrodes and water floods into the exhaust side and hydrolocks the engine lol

 

[mkast]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

For the amount of money you would spend, the results won't make you happy.

 

[mercruiser-mitch]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

For the amount of money you would spend, the results won't make you happy.

My mate builds custom exhausts, so all I would need to get would be an exhaust gasket to make a custom flange for him to weld a manifold up lol

Are there any off the shelf exhausts for the 3.0? All the upgraded exhausts I have seen are for the V8s and V6s. Where does everyone buy their exhaust componants from?

 

[Bondo]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

Where does everyone buy their exhaust componants from?

Ayuh,... For a 3.0l,..?? We Don't...

You DO understand that Boat Manifold MUST be Water-jacketed,... Right,..??

As everybodyelse has said,... You're barking up the Wrong tree...

 

[MikDee]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

My mate builds custom exhausts, so all I would need to get would be an exhaust gasket to make a custom flange for him to weld a manifold up lol

Are there any off the shelf exhausts for the 3.0? All the upgraded exhausts I have seen are for the V8s and V6s. Where does everyone buy their exhaust componants from?

I'm guessing you have a log type manifold with a 180 degree elbow at the back, going into the exhaust pipe to the prop with a rubber coupling. What you need to do is get a 90 degree elbow to bolt on in place of the U-shaped elbow (I really don't know if they make one? But, maybe you can adapt one off a V6, or V8, to fit) then just get some 3", or 4" rubber exhaust hose, and run it to the transom temporarily, then mark the outline on your transom, remove the hose, & drill out a hole, then put an exhaust tip in, and put it all together using double stainless hose clamps at each connection. Be careful that the hose does not interfere with your steering assembly at the transom before you do this! Actually First you'll need a rubber plumbing pipe cap 3", or 4", to cap the pipe to the prop, so no water backs up into the boat. You'll have to take a look at your situation to see if all this would work on your boat? And finally you did not get this from me, I disavow any knowledge of this info, and your actions

 

[mercruiser-mitch]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

Ayuh,... For a 3.0l,..?? We Don't...

You DO understand that Boat Manifold MUST be Water-jacketed,... Right,..??

As everybodyelse has said,... You're barking up the Wrong tree...

Which tree should I bark up? lol im very very very new to boats, why must they be water jacketed? surely they don't get UBER hot to warp and crack?

 

[Schmoe]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

Dude, trust me, there are thousands of 3.0 owners here and we've all thought of the same thing throughout the years. It's no secrete why the 3.0 has been Mercruiser's bread and butter for years, great engine, tough as nails, great fuel economy and pretty simple to work on. It's not, nor will it ever be, any thing thought up as a performance engine. Save your money and get another boat, or if you just love your boat and can't part with it, drop a bigger motor on it. However, beware the needs and problems that come with that......

 

[mercruiser-mitch]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

Ok, I just thought I would research into different ideas I was having, this is a dead end lol thanks everyone for the help

 

[ken_23434]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

About your question about the water in the exhaust...

Have you ever accidently touched a header under the hood of a car? The exhaust of an engine gets really hot. The water that cools the engine gets dumped into the exhaust risers to keep the exhaust components cool on the outside. Otherwise, you run the risk of burning anything that is near that exhaust (such as the rear of the boat where the exhaust passes through). Unlike a car, there is little to no airflow in the engine compartment of a boat.

 

[Bondo]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

The exhaust of an engine gets really hot.

Ayuh,... Usually from 1000? to 1200?,......
Although a lean condition can see nearly 1500?,... That's when the headers are Glowing Red....

 

[gadget73]

Re: Aftermarket/performance exhaust for 3.0 Mercruiser alpha one?

Compare that to the less than 200 degree surface of your typical marine manifold, and its a big difference. You can usually put your hand on those while the motor is running without hurting yourself.