Can a dry exhaust be routed through the prop exhaust route

[MWG2600]

Re: Can a dry exhaust be routed through the prop exhaust route

I have a set of gil marine offshore manifolds and pipes. used and cheep. They are water jacked, dry exhaust. What are you trying to gain from wet stock exhaust?

for what its worth there off a 30" spectre cat that had twin 454's would run 108mph. Thats why i ask what your trying to accomplish.

 

[Bondo]

Re: Can a dry exhaust be routed through the prop exhaust route

I have a set of gil marine offshore manifolds and pipes. used and cheep. They are water jacked, dry exhaust. What are you trying to gain from wet stock exhaust?

for what its worth there off a 30" spectre cat that had twin 454's would run 108mph. Thats why i ask what your trying to accomplish.

on a 5.7L

Ayuh,.... BBC pipes don't fit a SBC...

 

[MWG2600]

Re: Can a dry exhaust be routed through the prop exhaust route

Very good point Bond-o, I assumed he had a bbc since he wants to go fast.

 

[Bondo]

Re: Can a dry exhaust be routed through the prop exhaust route

Very good point Bond-o, I assumed he had a bbc since he wants to go fast.

Ayuh,.... I think/ thought the underlyin' goals are weight savin's, 'n noise reduction, in the boat's cabin....

I think dearmosd is missin' the differences 'tween water jacketed, wet exhaust, 'n dry exhaust....
Muchless, Where the exhaust is Dry, in water jacketed, 'n where it turns to Wet exhaust...

We also still don't know Where he's floatin' 'is boat.... Saltwater, or Sweetwater,..??

 

[Fun Times]

Re: Can a dry exhaust be routed through the prop exhaust route

But what type of cabin noise would these produce over the OEM manifold

Yes, having an header exhaust system would sound much different than the stock Merc exhausts you have now if you were going for a performance type sound---headers will be louder in general but really not as quite as loud as you would expect on the inside if ran through stock formation unless you went with a completely "dry" system/set-up, which you cannot do safely or legally especially in an stock format within an closed environment.

For additional information on headers, try googling "lightning headers marine".

 

[dearmosd]

Re: Can a dry exhaust be routed through the prop exhaust route

I guess im miss guiding everyone with the way im asking my question and im sorry for that.

-Freshwater only
-Pics were to display design versus specific items to be used. I know the first pic is of BBC headers and i have SBC
-NO chrome, ceramic coating at min.
-Goal is more weight saving purposes
-Dont want open end exhaust sound (i guess full dry exhaust with thru-hull design)
-Never stated want to go fast.


Goal, i will be building a fresh 5.7L stock bottom end, maybe new cam, now instead of iron heads/intake/exhaust manifold im looking into aluminum (for weight saving purposes, NOT specific for HP/go fast purposes)

Bond-o: When you refer to water jacket, what exactly makes it water jackets? Is the design a tube within a tube? So the otter tube allows water to flow around the inner tube (gases) hence cooling the exhaust and never allowing water to flow into exhaust port on the head. If this correct then this explains why the cost of aftermarket heads are what they are because of the extra work to build them. From the pictures you can not see the tube within the tube design therefor misleading me into a different design of this pic

Most after market affordable manifolds follow this design http://www.glmmarine.com/manifolds/images/Manifolds_Flyer_Web.pdf which i was under the impression is "wet-exhaust design"

So with the first and last pic, is this a tube with a tube design? If not how does the water flow within the design?

I understand weight difference is min but im exploring the area of saving maybe 10% weight (passenger capacity) not overall boat weight, thats like one less person in the boat.

I have some money saved up and plan on putting some into the boat, hence the fresh rebuild engine and i dont mind spending some money on the extras (aluminum heads/intake) easy enough but now exploring the exhaust manifold idea. Now from what i have learned so far is my idea of how the wet/dry systems work is wrong so thank you for pointing that out now i trying to correct myself and learn how the differences work, how does the water flow with the setup on the pic above (BBC style setup).

 

[Scott Danforth]

Re: Can a dry exhaust be routed through the prop exhaust route

yes, a marine exhaust is a tube within a tube. there is a water jacket around the exhaust pipes to keep the engine bay cool.

if you want to save weight, get a set of aluminum exhaust manifolds, however they can only be run in fresh water, or with fresh water cooling.

if your running aluminum heads, you also need to be only in fresh water or with fresh water cooling.

let me explain the tube headers simply in the picture above. take a simple beer can, call it the exhaust pipe. put that beer can inside of a coffee can, call that the outer water jacket tube. now put water in the coffee can, but not in the beer can.

here is a picture. the red is the exhaust path, the blue is the water path http://revolutionmarine.com/shopsite_sc/store/html/media/cutaway480.jpg

Now the experience and equipment to build tube within tube headers that work, dont burn up your boat, dont corrode, and dont fatique crack is why they cost $2400 for a small block.

 

[dearmosd]

Re: Can a dry exhaust be routed through the prop exhaust route

Well the little unknown part has been exposed and it all makes sense to me know. I know where I went wrong on the idea and as much as I feel stupid it’s all a learning process.

The idea of the tubing (wet exhaust) has been abandoned and looking into cast aluminum. Since this boat is going to be freshwater only, I went and found a set of aluminum heads from a friend of a friend who deals with used auto parts and found a set of aluminum vortec heads that are bare for $400(pr), cleaned and decked just need the hardware and a used Edelbrock performer for $120.

With all the info that I just learned I’m leaning towards just a cast aluminum manifold. I’m waiting to hear back from the manufacture or the distributor about actual weight of the manifold and riser and if the weight savings is worth the price I will get a set for around $650-700.

So for the upgrade about $1200-1300 and as i receive the parts i will weigh the old parts and the new and see what the difference really is.

Thank you for all the help on clearing up the confusion i had on the exhaust idea. But as i though i needed to be educated on how exactly all the designs were really.

 

[Howard Sterndrive]

Re: Can a dry exhaust be routed through the prop exhaust route

aluminum weighs less, sure, but watch a boat cruising down the lake. It's the bow that rises and the mid section of the boat that needs the most lift to plane.
Knocking weight off the engine won't hurt, but it all seems like a huge waste of time. Why do you want less weight if you don't want to go fast?
At cruise speeds, there will be no measurable difference in fuel economy when that 200 pounds is removed from the stern. The engine is at the fulcrum of the boat where the drive is anchored in the water. It needs lift, but it's not super weight sensitive.
Unless you work for an aluminum company or something, and want to use it for marketing, cast iron is just fine.

 

[dearmosd]

Re: Can a dry exhaust be routed through the prop exhaust route

i guess im addicted to projects and wanting to be different. I guess i can say adding and extra battery and two subwoofers/boxes added weight to the rear and now im recooping the weight back from the engine area.

 

[Bondo]

Re: Can a dry exhaust be routed through the prop exhaust route

Well the little unknown part has been exposed and it all makes sense to me know. I know where I went wrong on the idea and as much as I feel stupid it’s all a learning process.

The idea of the tubing (wet exhaust) has been abandoned and looking into cast aluminum. Since this boat is going to be freshwater only, I went and found a set of aluminum heads from a friend of a friend who deals with used auto parts and found a set of aluminum vortec heads that are bare for $400(pr), cleaned and decked just need the hardware and a used Edelbrock performer for $120.

With all the info that I just learned I’m leaning towards just a cast aluminum manifold. I’m waiting to hear back from the manufacture or the distributor about actual weight of the manifold and riser and if the weight savings is worth the price I will get a set for around $650-700.

So for the upgrade about $1200-1300 and as i receive the parts i will weigh the old parts and the new and see what the difference really is.

Thank you for all the help on clearing up the confusion i had on the exhaust idea. But as i though i needed to be educated on how exactly all the designs were really.

Ayuh,.... Just a heads up,... Not all Chevy heads are the same,....

Ya need to know the combustion chamber volume to figure the compression ratio, 'n intake runner lengths can play 'ell if to big on a marine motor...
In other words, a SBC can be built to do Lota different things, 'n parts have to be match, so's they'll play together well...

 

[QC]

Re: Can a dry exhaust be routed through the prop exhaust route

He's past that, Bubba. Back to typical Marine, just going with aluminum.

 

[emilsr]

Re: Can a dry exhaust be routed through the prop exhaust route

i guess im addicted to projects and wanting to be different. I guess i can say adding and extra battery and two subwoofers/boxes added weight to the rear and now im recooping the weight back from the engine area.

That makes sense, although still not sure what your goals are.

Do yourself a favor and put the same kind of research in your motor build. A 6k rpm street screamer won't make a good boat engine. You're looking for more of a truck engine; low rpm torque, max rpm of 5k. Lots of guys have had good results stroking to a 383. Your Alpha drive can live if you stay away from full throttle holeshots and air time.

 

[dearmosd]

Re: Can a dry exhaust be routed through the prop exhaust route

Goal: Less weight and more of a fresh engine, it came to me as unknown hours on the motor, the guy I got it from was a mechanic but that doesn?t mean he took care of his stuff. I know torque is more than HP on marine engines and with the rebuild it will most likely be a more or less stock rebuild, if anything a different cam if I can get heads air flowed and a cam to match that, but I?m a little scared to do the 383 as it will provide more torque but only have had outboard motors in the past so I would scared to spend the money on a 383ci and blow the outdrive. Although knowing about SEI outdrives I feel that is an affordable option as a replacement but.... not sure if I want to take the chance. People say Alpha one will hold up to a 383ci with conservative throttle action but..... The known slight incompatible combo, not sure if I want to learn with that combo.

The boat is a 98 Bayliner Capri 2050LS roughly 2400lbs (more with fluids and people) and I usually have 6 adults or 4 adults and two kids, the kids are getting old enough to start tubing and maybe knee board so towing is my goal now, speed not so much, but I also want to plane with as little speed as possible as the young ones are only 7 yrs old and still learning to swim (well learning to be better), so speed on a tube still scares them a little. I ripped the rear floor and stringers out last year before deploying with the Army (soon to return) and the boat is worth more as a functional family fun ship versus a show piece so. I traded a 390RWHP, 1997 Trans Am for this boat so I know about wasting money but it was for the family. Couldn?t fit the kids in a two seater car. Any who, I miss the motor modding and this is my only motor to play with and I would like to start fresh and know how to work around and take care of it till I?m able to afford the next level of boat ownership (something more new).

So the heads are said to fit the block I my friend picked for me from a 97 Yukon with 70K miles for $250 (crank, pistons/rods). Now the heads specs are 180cc runners, 64cc combustion chamber, 2.02/1.60, I?m asking about the intake degree angle and waiting to hear back on the brand (now sounds too good to be true so?.we will see). But I?m looking into HGE aluminum manifold/risers.

 

[RogersJetboat454]

Re: Can a dry exhaust be routed through the prop exhaust route

So the heads are said to fit the block I my friend picked for me from a 97 Yukon with 70K miles for $250 (crank, pistons/rods). Now the heads specs are 180cc runners, 64cc combustion chamber, 2.02/1.60, I’m asking about the intake degree angle and waiting to hear back on the brand (now sounds too good to be true so….we will see). But I’m looking into HGE aluminum manifold/risers.

Are these the fabled Aluminum Vortec heads? Factory heads for that Yukon would be cast iron. GM, and other manufacturers have since cast Vortec style heads in aluminum for performance enthusiasts, but were never factory equipment.

Is he sure the vintage of that engine is correct? The later LS engines would have aluminum heads, but are in no way compatible with the old SBC format.

 

[dearmosd]

Re: Can a dry exhaust be routed through the prop exhaust route

heads are the specs only im still waiting to confirm the exact brand and model. The Yukon is block/crank/rods/piston only no top end.

The head spec i listed were of the aluminum that my friend said he knows a guy who said they were but waiting on brand and model # to confirm actual specs of the heads. The block didnt come with any heads

Im exploring the ease or not of just going aluminum heads (non-vortec) heads, that will still be paired with either stock mercruiser 350 cam and deliver around 300HP no more than 325HP at the crank, not sure were the torque will be with this combo. The engine builder is doing his research on the combos also since i have a HP/torque limit im trying to stay around, he says most people want as much as the parts can produce so waiting to hear what he has to say.

Question: Everyone talks about HP limits with the Alpha one drive but whats a safe torque number?

 

[emilsr]

Re: Can a dry exhaust be routed through the prop exhaust route

Question: Everyone talks about HP limits with the Alpha one drive but whats a safe torque number?

That's a very good question, but not sure there is a good answer. Mercruiser doesn't talk torque, nor do they even publish torque curves (that I know of). Everything is about horsepower on paper.....but....

The boat's weight also matters as the heavier boat will be harder on drives. For example, the 350mag (300hp) was offered with both an Alpha (lighter boats) and a Bravo (heavier boats). With your boat (and what you're doing with it) I think you're smart not to build much more torque than it came with from the factory. Stick to a 5k rpm redline and your drive should hold up fine.

Boat ownership will provide you all the maintenance and cleaning a guy could want; no problems there.

Sounds like you're on the right track, just be careful about using hot rod tricks on a boat engine;....that's all I'm saying.

 

[QC]

Re: Can a dry exhaust be routed through the prop exhaust route

There are a variety of reasons that boat manufacturers don't talk torque. Too much for this discussion. What is pretty much clear though is that with the limitations of the cam shape you pretty much get what you get. Also, there is virtually no way to keep the engine operating at peak torque levels in a marine application, you simply push right through it (getting on plane). The only way that you could subject the engine to peak torque for extended periods of time would be to over wheel so she couldn't exceed peak torque RPM. Mash the throttle, get stuck at say 3400 RPM, and leave her there. Yes, if you mash the throttle for hole shot you will pass "through" peak torque. If you are powered in the way you are, you will accelerate past there pretty quickly, and not really exert that direct force on the drive. Not to say you shouldn't be soft handed; you should be...

 

[dearmosd]

Re: Can a dry exhaust be routed through the prop exhaust route

Sounds like you're on the right track, just be careful about using hot rod tricks on a boat engine;....that's all I'm saying.

i guess i should reframe on using words like modding with marine application, i more meant changing things up (i more stock/slightly altered way) to make it my own. Thats kinda why im going aluminum and paint the block, change valve covers....dress things up to a more custom look, the specs see to have to be a more stock things or parts wont want to play nice with each other.

Thank you all for helping me correct the issue with the exhaust and help keep other things in mind when i build the fresh motor.

 

[81 Checkmate]

Re: Can a dry exhaust be routed through the prop exhaust route

Been reading and following this thread - Just my thoughts!

Reading about the ill - fated 470 stories...Alum head on a cast block in a Marine aplication....... One - overheat and that motor is done. I would have to pass on this one.... All that Money spent for a few less pounds in a 20 ft boat. I cant see it.

I would take that money and buy a new short block.....some cast iron vortec heads/Alum intake combo... and be done with it.

You will have a nice strong motor for your family and future.

Good Luck!