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Old     (chicksdigflips)      Join Date: Jul 2011       11-30-2011, 7:07 AM Reply   
Just wondering who owns a newer epic with the 8.2l or 8.1l. how bad on gas is it compared to say a 5.7 that you ride a loaded down boat
Old     (rallyart)      Join Date: Nov 2006       11-30-2011, 7:27 AM Reply   
Not much difference, except when you go full throttle. When you are running it takes the same horsepower, and so the same fuel, with any engine almost.
Old     (lifetimewarranty)      Join Date: Oct 2008       11-30-2011, 7:39 AM Reply   
Some guys have said that they are actually more efficient since they have so much torque and can run lower rpm's than the small blocks (while doing the same task).

Seems to work the same with towing with that engine. My brother has one in a Suburban. 200k plus miles and zero issues with it.
Old     (timmyb)      Join Date: Apr 2007       11-30-2011, 7:45 AM Reply   
My friend has an '07 with the 8.1 Volvo and I don't think he uses any more gas than I use in my Tige that has the 5.7 marine power in it.
Old     (simplej)      Join Date: Sep 2011       11-30-2011, 10:47 AM Reply   
i think it will have more to do with the hull. I would guess youd use less gas than a 5.7 when fully weighted and more gas than a 5.7 when just cruising
Old     (norcalrider)      Join Date: Jun 2002       11-30-2011, 11:10 AM Reply   
Quote:
Originally Posted by lifetimewarranty View Post
Some guys have said that they are actually more efficient since they have so much torque and can run lower rpm's than the small blocks (while doing the same task).
As I understand marine engine peak gas consumption efficiency is not based on lower RPMs. Different camshafts affect RPMs and it really depends on the sweet spot that specific engine is engineered for. There are a lot of factors that lead to peak efficiency on boats and I do not think RPM is one of them.
Old     (cadunkle)      Join Date: Jul 2009 Location: NJ       11-30-2011, 11:40 AM Reply   
RPM is a factor, as is the cam, ignition timing, induction setup, tune, enrichment, exhaust, head design, port flow and velocities, chamber design/quench, etc. Generally a bigger engine in the same hull will not consume a large amount more fuel at a given weight. At a lighter weight the difference will be larger though. Other factors include engine life and wear. A big block, even a BBC, will last longer and wear better pushing a big hull with a lot of weight than a small block. It can push the weight at a lower RPM (prop) and with less stress on components. Higher RPM wears out engines. The rods stretch and compress more at higher RPM, of course dependant upon rod design and piston weight. This wears rods and also bearings. Oiling can be a problem at sustained higher RPM in unmodified blocks. There are many factors, but in mild low HP applications like any typical marine engine in a ski/wake boat I don't think a big block will burn a huge amount more fuel than a small block in typical use, it will likely be noticeable though.
Old     (lifetimewarranty)      Join Date: Oct 2008       11-30-2011, 4:55 PM Reply   
Quote:
Originally Posted by norcalrider View Post
There are a lot of factors that lead to peak efficiency on boats and I do not think RPM is one of them.
I'll have to agree with Cadunkle here. Basically, (as others have said) in a normally sacked out wakeboat your 5.7 or similar motor may run at 4k rpm(let's not argue this number)...where the 8.1 motor may be running at 3k rpm...again, just a guess. As cadunkle explained, the bigger motor is not working near as hard, and so parts are happier and economy will be better...now I am not saying it should get better economy, just that the difference may be negligible. (some may have said it, or hinted at it, or danced around it, or stepped in it, I am just relaying it.)

It seems that when towing with the 8.1 (in the suburban), the economy is really similar to what I get with my 5.7 tahoe - and I would much rather have the bigger motor then.

iow, just because the motor is bigger, doesn't really mean you use (too much) more fuel in a heavy boat application. If you run around empty and pull tubes or ski or joyride, then we have a different story. The bigger motor will gulp way more imho.

But, yes...there are many factors...
Old     (talltigeguy)      Join Date: Sep 2003       11-30-2011, 6:08 PM Reply   
I owned a Tige 24V with a 5.7 and a MC X45 with the 8.1.

I loved the 8.1 and it did not groan, no matter how much weight was in it. The Tige had a limit on how much I could put in it and still get out of the hole reasonably.

My MC X45 got about 12 GPH when wakeboarding with a total of 2200 pounds of ballast (stock + 1200+/-) and only 2 people in the boat.

I hate to go against guys above who sound so much smarter than me, but the 8.1 took substantially more fuel than the 5.7, doing the same task, whether it was tubing, wakeboarding or surfing. But the 8.1 could handle excess weight like no other.

Chicksdigflips, knowing that you got a great deal on a new boat, you still dumped at least 40-50K on the boat, gas is small change, relatively speaking. You said you put lots of extra ballast in your Axis, and I am sure you will load the Epic up heavy, so plan on paying a nice gas bill.
Old     (cwb4me)      Join Date: Apr 2010       11-30-2011, 6:25 PM Reply   
Think of an engine as a air/fuel pump.8.1 litres of mixture per RPM vs 5.7 litres of mixture per RPM.All RPM'S being the same the bigger motor uses more fuel.Since wakeboats need torque the bigger motor produces more Torque at the same RPM.Therefore it can handle a more agressive prop at the same RPM.With the right prop the bigger motor can be more efficient.So many different factors it's really hard to say.
Old     (lifetimewarranty)      Join Date: Oct 2008       12-01-2011, 8:10 AM Reply   
Quote:
Originally Posted by cwb4me View Post
Think of an engine as a air/fuel pump.8.1 litres of mixture per RPM vs 5.7 litres of mixture per RPM.All RPM'S being the same the bigger motor uses more fuel
I think we all get that...but it isn't the end of the story. There is a huge difference in the mixture though. What if you have 2 four barrel carbs and 2/3's throttle at 3krpm on the small block vs stock fuel injection and 1/3 throttle at the same rpm on the big block...that would make for some dynamically different fuel mixtures (just a scenario).

Like I said, on the Suburban, when towing, there is very little difference between it and my small block tahoe...(big difference when not towing, driving in town, and have a lead foot!) but, Tall tigeguy has the only boat scenario so unless he wasn't propped appropriately or there were some other issues, I would have to go with his analogy.

I would assume that the OP has done a bunch of searches about GPH with the Epic guys and compared that with info from small block GPH guys (Personally, I have no clue what my boat uses...lol)

Chicksdigflips - if you know exactly what the Axis was using GPH, post some info once you get it on the Epic. First hand knowledge is welcome.
Old     (cadunkle)      Join Date: Jul 2009 Location: NJ       12-01-2011, 9:14 AM Reply   
Robert, other factors include load on the engine and enrichment. The less load the engine sees, the less need to enrich the mixture. A longer stroke and more displacement will make more torque at a given RPM. The more torque, the less the need for enrichment... Be it a power valve on a Holley, needles raising in the jets on an ABF style, secondaries opening more, or a longer injector duty cycle on a fuel injected engine.

Also lugging the engine at a lower RPM (overloaded for the HP/torque and prop/gearing) can result in detonation. On an regular engine with normal distributor this can result in engine damage, cracked piston ring lands, hammering the rod bearings and rod journals on the crank. On an engine with a electronically controlled distributor this will result in the computer pulling timing once it senses detonation (knock sensor on your block). Once timing is pulled the engine will need a richer mixture to run properly, so the ECM will also give a longer duty cycle on the injectors when pulling timing under load at cruise or higher RPM.

From this you can see how turning a higher RPM (gearing/prop) resulting in less load that the engine sees can result in lower fuel consumption from additional timing and leaner mixture as opposed to a lower RPM with less timing, less enrichment, and possibly less throttle opening. Greater air velocity also results in greater fuel atomization, torque and efficiency. Look at heads set up for trucks or lower RPM applications. The intake ports are smaller, to promote high intake charge velocity. Engines designed to make power at higher RPM have larger ports, which is a contributing factor to sluggish low RPM performance.

Once thing to look at when comparing different engines and different builds is brake specific fuel consumption across the RPM band. This can help you determine the most efficient RPM to run but not necessarily where you will burn the least fuel.
Old     (cadunkle)      Join Date: Jul 2009 Location: NJ       12-01-2011, 9:27 AM Reply   
Quote:
Originally Posted by lifetimewarranty View Post
I think we all get that...but it isn't the end of the story. There is a huge difference in the mixture though. What if you have 2 four barrel carbs and 2/3's throttle at 3krpm on the small block vs stock fuel injection and 1/3 throttle at the same rpm on the big block...that would make for some dynamically different fuel mixtures (just a scenario).
No, running dual carb vs a TBI or MPI setup wouldn't change fuel mixtures. A given engine build will need the same mixture to run at peak performance, the engine doesn't care how it's getting the fuel, only that the mixture meets the requirements of the given load, RPM, timing, etc. Carb and EFI both do this effectively and comparably. There will be minor differences between different models of carbs and different types of EFI setups.

Aside from that, there wouldn't be a huge advantage to running a dual carb tunnel ram style setup on a low RPM torquey wake boat engine. You'd be running very small carbs to keep proper velocity through the carbs and still have a stall of the intake charge given the large plenum volume of a tunnel ram or even a highrise style dual carb intake. It would be a mismatched combination that would result in a general all around poor running engine in that application.
Old     (norcalrider)      Join Date: Jun 2002       12-01-2011, 10:19 AM Reply   
Engines are most efficient at peak torque. Marine engines are designed to run at higher RPMs for a long duration unlike cars and trucks that are geared and intended to drop to lower RPMs using less HP to maintain speed. Marine engines are always loaded and most efficient at higher RPMs than automotive engines (gearing negates the need for torque). I'm not arguing that marine engines are meant to redline just that their most efficient RPM is higher than that of a car or truck. That is how they are designed. My assertion is that propped correctly the 5.7 will be more efficient. Whether that difference is significant would require some analysis. That being said the hole shot on a big block is probably significantly more desirable.
Old     (lifetimewarranty)      Join Date: Oct 2008       12-01-2011, 1:08 PM Reply   
Quote:
Originally Posted by cadunkle View Post
No, running dual carb vs a TBI or MPI setup wouldn't change fuel mixtures.
Perhaps it is I who am missing something here. Are you saying that a vehicle that is running a small block with 2 big 4 barrel carbs and a lot of throttle will be the same fuel mixture as a big block running very little throttle?

All I am trying to suggest is that a smaller engine that is at 2/3 or 3/4 throttle vs a large engine at 1/4 throttle may have similar fuel consumption...but Maybe I am dissecting this too much

I'm surprised that there aren't some strings here that have some GPH and weight numbers for us to see...
Old     (cadunkle)      Join Date: Jul 2009 Location: NJ       12-01-2011, 2:39 PM Reply   
Tim, carbs have several circuits that work together, progressively. Take a Holley double pumper for example. You have an idle circuit, a transition circuit (transition slots just above idle discharge hole), main circuit (main jets), and enrichment (power valve). There circuits are progressive and build on top of each other. You have different jetting on primary and secondary sides. The secondary side may or may not have a power valve. Both primary and secondary have accelerator pumps either 30cc or 50cc and may have different accelerator pump cam profiles and discharge nozzle sizes to give differing rates of enrichment to prevent a momentary lean condition when opening the throttle, until airflow through the venturis increases. Depending on the model of carb some or all of these circuits are tunable.

At light cruise you are on main circuit which is primary jets (+idle+transition, though they only contribute small amounts of fuel). Some more throttle and you may start to crack the secondaries, adding secondary main circuit (larger jets) for moderate enrichment. Open the throttle some more and your power valve(s) will start to open, resulting in additional enrichment (idle+transition+primary main+secondary main+power valve enrichment). The same could be said at that same light cruise but instead of accelerating, just add more weight. Add 1000 lbs and you may start to crack the secondaries, add 2000 lbs and you may open the power valve. You want the carb tuned t

The carbs on such a setup, a small engine with dual carbs running 2/3 throttle at 300 RPM would have to be quite small. Likely a pair of 450 CFM Holleys... Which would still be way overcarbed for a ~350 cube small block Performance would suffer down low from low air velocity through the boosters. Idle might be erratic or rich, it would respond slowly to rapid throttle changes, would require some interesting accelerator pump tuning to mask the lean bog, etc. It's just not a setup matched well for a small engine that is built to start building torque down low and have a fairly flat torque curve. Throw some big carbs on there, 750-1100 CFM and the thing would run so poorly it wouldn't be very drivable.

To answer your question... Yes, a vehicle with a small block with dual carbs will in fact have the same fuel mixture as a big block. It will require a similar mixture under light load and a similar mixture under heavy load. If we're talking same hull and same ballast, while still keeping the same RPM at a given speed the small block engine will require more airflow and a richer mixture. You respond by opening the throttle more, getting into the secondaries for further enrichment and possible ending up cruising on the power valve if vacuum drops below the power valve's rating (manifold vacuum is an indication of engine load, the lower the vacuum, the more the load). This will result in similar or worse GPH than the big block that is able to pull the same load at the same RPM and speed but at a leaner cruising mixture.

Now say we drop a powerslot trans in the small block boat. Gear ratio changes from direct to 1.23:1. The small block will now turn 3700 RPM. Say we drop an inch on the prop pitch and (for argument sake) bring RPM to 4000 at the same MPH at the big block boat. Now the small block is able to climb to a higher RPM where it will make more power. The small block now has a lighter load to pull than the big block, through mechanical advantage (gear reduction). At that point it may take more throttle opening, 2/3 for argument's sake, than the big block boat. The difference is that with a lighter load on the engine, it will hold 4000 RPM without getting into the enrichment circuit (power valve). The smaller engine will burn less fuel when geared properly, but probably slightly or negligible less than the big block.

Bottom line, carb or EFi doesn't really matter. If tuned well they will have the same GPH. The engine has the same exact CFM and mixture requirements whether it's EFI or carb. Eith EFI or carb, the smaller engine will be running a richer mixture when it sees the same load as the bigger engine.

For GPH numbers, my numbers may not mean much... But my Saltare with 454 and 800 CFM double pumper will do 21 MPH at 2300-2400 RPM IIRC. Boat dry is 3500 lbs according to Supra, plus 4 people and 800 lbs approx 6-7 GPH in my unscientific hour meter vs gallons at fillup calculations. My carb is slightly rich on jetting though, which I'll fine tune when I have a day on the water that I can spend time on that by myself. There's a guy on the Supra forums with a small block Saltare, same exact boat as mine. I'd be curious to see what he gets for GPH running similarly.

I don't think many newer boats had both big block and small block as an option in the same hull? Typically it seems most stuffis small block with some minor changes to the engine to squeak 20-30 more HP out of the same engine as a higher priced option. If you look at those engines dyno charts I would expect the higher HP engines don't have a very different torque curve than the smaller HP engines since they are the same displacement.
Old     (redsupralaunch)      Join Date: Aug 2002       12-01-2011, 6:37 PM Reply   
Here is another way to look at it.

"just a note, since i was in the engine biz for 20 (long) years, i learned that all engines burn pretty much the same amount of fuel. Sound goofy? I may be a little off but i'll use the old figures (pre EPA tier 3 requirement). An engine will use around .425 lbs of fuel per brake hp hour. In other words. A load that requires 150hp to accomplish the "work" will burn 150hp x .425 divided by 6.8 (the weight of the fuel)= (150x.425)/6.8 or 9.3 gallons.

Soooooo, if two boats with the same hull design and coefficient of drag, etc, loaded with the same amount of ballast will require the same hp to push it whether its a 5.7 v8 or an 8.2 v8. or even a 4.3L inline 6, 150hp burns that amount of fuel with only miniscule variances. Where you start to see any differences is in the upper or lower 20% of the hp curve. i.e. a big block 8.2 will burn more at it's lower 20% than a smaller engine since the big block has more mass to move that is not contributing to the "work" while a smaller engine will burn more at it's upper 20% of the hp curve since it's efficiency is way down and the physics of the cumbustion chamber are maxed out...the hp curve starts to drop.

this means that given similar load requirements a 5.7 and an 8.2 burn the same fuel in the most common hp requirement ranges of our sport. Downside is that an 8.2 does burn more at surf speeds. But in some instances, it will burn less at loaded up wakeboard speeds." Greg Smith, National Sale Manager, Epic Boats


I love this engine. We used the 8.2L at 2011 USA Wakeboard Nationals where Team USA members Austin Hair and Raquel Hoffman took podium. This is one bad ass engine! PCM, Illmore, nor Indmar have it. Merc did the R&D to get the CAT exhaust and O2 sensors on a big block. You can really tell how much more lean it burns compared to the 8.1 that was discontinued by the other manufactures. Fuel economy goes up with a CAT. This was very proven when Indmar did the first CAT in '07. Bottom line is you have to supercharge the aluminum 6.2L to get this much touque which btw doesnt have CAT.

About CAT: you only need one call you to tell you that a child just died due to Carbon Monoide poisoining behind a your friends boat to forever change your mind about them. I got that call a few years ago.
Old     (lifetimewarranty)      Join Date: Oct 2008       12-02-2011, 7:41 AM Reply   
Thanks for that post Chris - and for all that insight. I, for one, don't have to justify a cat. Seems obvious if you drive behind even one car without it I am gagging from fumes vs a thousand cars on the highway and you hardly smell anything.

Seeing how our sport has the habit of putting us behind a high horsepower motor the entire time we are doing it makes it even more obvious.

Cad - thanks for the explanations. I think we were trying to say the same things ( when I compared the suburban 8.1 towing to my 5.7)...but evidently mine got lost somewhere in translation...
Old     (fredlap)      Join Date: Jul 2008       12-02-2011, 8:37 AM Reply   
I didn't read anything but I have to talk about my last summer on a Epic boat. There is no comparaison with a 5.7L. The 8.1L is a endless hole! With the slammed Session Si, it was like 33 to 38$/h. My friend 210 is about the same. With the epic it's around 50 to 60$/h. I'm always putting gas in it! But you know what? I don't care because if it's the the prive for this wake, I will live with it! It sucks but I'm so pumped each time I hit this wake!
Old     (norcalrider)      Join Date: Jun 2002       12-02-2011, 10:23 AM Reply   
Quote:
Originally Posted by redsupralaunch View Post
Fuel economy goes up with a CAT. This was very proven when Indmar did the first CAT in '07.
This doesn't make sense to me. Any data or further explanation?
Old     (rallyart)      Join Date: Nov 2006       12-02-2011, 1:01 PM Reply   
Catalytic converters require a full closed loop system so the engine management if more sophisticated. It should not be much of a change.
Old     (ScottR)      Join Date: Aug 2011       12-05-2011, 7:23 AM Reply   
Wow, great info in here. I had an Epic with an 8.1 and now one with an 8.2 and honestly don't see any difference in how much fuel is used. I got one full summer with the 8.1 and just got done with one full summer with the 8.2 Wish I held onto my gas receipts because we put almost exactly the same hours on both boats. I would imagine we put just a bit less gas in the 8.2. Just a gut feeling. I agree with whoever said, (Gas is small change when compared to the cost of the boat)

Great info from some very smart guys in here!
Old     (HighVoltage)      Join Date: Aug 2010       12-05-2011, 10:09 AM Reply   
I've taken out epics with the 5.7, 8.1, and 8.2. The 5.7 does use less fuel, but it also does not accelerate as fast. There is enough power to move it around though. If you fill up the ballast tanks and add some fat sacs, the 5.7 will start to struggle.

The 8.1 and 8.2 use pretty much the same amount of fuel. But the 8.2 is a bit more refined of an engine.

Like other have said, when your boat costs as much as these do, gas is not the primary concern and I would go with the bigger engine. Plus, if your just going out to cruise, you can throw a tall pitch prop on the 8.2 and run 60mph no problem
Old     (lifetimewarranty)      Join Date: Oct 2008       12-05-2011, 5:15 PM Reply   
Quote:
Originally Posted by HighVoltage View Post
you can throw a tall pitch prop on the 8.2 and run 60mph no problem
Not doubting it...but we need some videos of that!
Old     (ScottR)      Join Date: Aug 2011       12-06-2011, 6:41 AM Reply   
I am with TIM, can you prove that! One thing I hate about inboards in general that are built for surfing and boarding is that max speed is only about 33 or in that ball park. Would love just to get even 50 out of her. With my 8.2 sure seems like I should be able to do that.
Old     (monkey_butt)      Join Date: Sep 2011 Location: Twin Cities       12-18-2011, 7:15 PM Reply   
Scott, was looking at your boat most of the fall but have gotten a sweet deal from Epic on a 2011 23V with the 8.1 engine - couldn't resist. Based on that you had them both barely a season apart - how much did the noise volume change? My prior boat was an Epic with the 8.1l Volvo and I had the fresh air exhaust on which helped a lot with the exhaust fumes (you got high within a few minutes when surfing) and it also reduced the engine noise but I wonder how the 8.2 compares against the 8.1? My boat is basically the same you have - as said - the only exception is the engine.
Old     (rdlangston13)      Join Date: Feb 2011       12-18-2011, 9:43 PM Reply   
i know this is completely off topic but i have a 08 moomba lsv with a 325 indmar with no cats, normal exhaust and i have never even gotten light headed or notice the exhaust fumes while surfing.

how long do the surf sessions last for yall to be having CO problems???
Old     (asdfgboy)      Join Date: Dec 2011       12-19-2011, 6:51 AM Reply   
Yes sir can you answer the above question?

Quote:
how long do the surf sessions last for yall to be having CO problems???
Also, I want to know the answer? Thanks
Old     (ScottR)      Join Date: Aug 2011       12-19-2011, 8:05 AM Reply   
Nic,
I can honestly say the 8.2 is much more quiet that the 8.1. I am not a mechanic at all so have no idea why that is but I assure you it is. I too had a 2011 with a FAE on it and was in love until I got the 8.2 I don't have an FAE on this nor will I put one on. I have no issues with exhaust at all and put my kids back there on a board and have zero worry when doing so. I can't smell a thing. Did you get the same color scheme?

My boat is for sale again...FYI.... so anyone wanting a smoking deal on a 2012 Epic with 54 hours on her, hit me up. Scott.robinson.nysq@statefarm.com Sorry didn't mean to steal the thread.....
Old     (redsupralaunch)      Join Date: Aug 2002       12-19-2011, 10:11 AM Reply   
Sound: Yea the CAT(s) act like a muffler and is more quite.
Smell: While surfing, I have always found the smell in the rear seating area was far worse than on the wake.
Old     (monkey_butt)      Join Date: Sep 2011 Location: Twin Cities       12-19-2011, 10:47 AM Reply   
Scott - thanks for the reply - as said - was looking at yours for most of the fall and had I not gotten the sweet deal we would have been talking already ... but no - I got the brown one which was probably my least favorite color at first ... people complained that the interior was beige/grey and wouldn't match the outside etc. I posted a few pics on another thread to show the actual color - it's actually beige/tan which does match the outside well but neon lighting distorts the color when taking pictures. So I'm already talking to Larry Mann to get a FAE installed - wasn't sure if it would be necessary but you pretty much confirmed that the issue is still there.

Now it's back to modding around for the winter - glad I got the surf trim tabs standard - so that has been taken care of. Boost box for volume control is first - more LED in the boat (speakers etc) and underwater lighting in the first round. Plus have to take out the back seats - was hoping that Epic solved the issue with the water accumulating in the rear back seat corners but that's still the same as it was with the 2007 - collects water and ultimately stains the vinyl. So will drill holes again there and run drain lines into the bilge - hopefully Epic solves this next year or so.

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