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View Full Version : 8 Litre versus 6 Litre


Springer
09-30-2007, 05:45 PM
Does anyone have any experience with both these motors. Is the 8 litre 425 HP or 450 HP? What about torque specs on both

Ski-A-Rees
09-30-2007, 06:09 PM
Are team has an 2006 PS 190 with the 8.1 liter and wow does it rock the house! It's 450 HP and it has the quickest acceleration of any inboard I have been in. I don't think anyone really needs an 8.1 unless they are part of a show ski team.

prostar205
10-01-2007, 12:42 PM
Springer -

The horsepower rating on the 8.1L engines changed in 2003 to 450hp. Prior to that, it was 425hp.

As for the need for an 8.1L - I would say HELL YES, you need an 8.1 engine in these bigger boat X-Star, X-30, X-45 if you are going to load them up with ballast - 2,000+ lbs and about 5-6 of your buddies. I completely agree that an 8.1L is overkill for a 197 or 190. I did not even know you could get that engine in those little boats.

I have an '02 X-30 with the 8.1L motor and I would not have anything less.

Diesel
10-01-2007, 01:39 PM
Paging MYMC.....another 8.1L vs. all other justification/smack down needed in general discussion.

Jim@BAWS
10-01-2007, 01:46 PM
L Bruner's 190 with the Sarasota Ski a Rees came from us at BAWS
WHAT AN ANIMAL. Larry was lucky...just happened to have one in stock
A CLOSED BOW 190 w/ an 8.0....Yeah we floor plan 2 or 3 of those a year YA RIGHT HA HA HA

You can see the boat in this months WATERSKIER. USA WATERSKI MAG.

The New 6.0 in the X-Star is an AWESOME package also TONS OF POWER

Jim@BAWS

SummerObsession
10-01-2007, 02:02 PM
Like they always say in drag racing (my theory as well):

"There's no relacement for cubic inch displacement!!"

Words to live by, for sure.

MYMC
10-01-2007, 02:33 PM
Paging MYMC.....another 8.1L vs. all other justification/smack down needed in general discussion.
My arm is too tired for this anymore...

PendO
10-01-2007, 02:35 PM
mike, less arm, more wrist

anyways ... for those who want the engine hp/tq curve, here it is

PendO
10-01-2007, 02:38 PM
.........................................

and if you can't open a *.pdf then here it is in *.jpeg

MYMC
10-01-2007, 02:39 PM
mike, less arm, more wrist

anyways ... for those who want the engine hp/tq curve, here it is
I'll give it a try...

PendO
10-01-2007, 02:42 PM
...........................

die horse die!

PendO
10-01-2007, 02:44 PM
*.pdf mcx v. L18

prostar205
10-01-2007, 02:48 PM
Putting any small block motor up against the monster L-18 is just an unfair fight. People to talk fuel economy, but let's be real here folks - who buys a boat for fuel economy. I spend $500 per month on fuel on my boat and I would like to spend more. That means I am actually using the boat.

I say if the L-18 is available, get it. No questions asked.

MYMC
10-01-2007, 03:48 PM
Putting any small block motor up against the monster L-18 is just an unfair fight. People to talk fuel economy, but let's be real here folks - who buys a boat for fuel economy. I spend $500 per month on fuel on my boat and I would like to spend more. That means I am actually using the boat.


First, in a wake application (i.e. ballasted) the big block will knock down about the same HPG (hours per gallon) of the little engines...so the argument rarely comes down to fuel usage, it's more about upfront cost. I have explained ad nauseum how the L-18 not only improves the performance of the boat but also the resale value; however, this question comes up at least once a week...soon the "my MCX is plenty and I run 5000lbs of ballast over stock in my X-Star" people will chime in along with the "Rusty runs a 310 and it'll pull your arms" off crowd chime in to spoil the big block love. However, the fact remains that from the X-Star up, the performance benefits of the LY6 and better yet the L-18 cannot be over stated.

You may now return to horse beating!

ProTour X9
10-01-2007, 04:56 PM
I wish our boat had an L-18...........:(

Springer
10-01-2007, 11:42 PM
Thanks so much for getting the power comparison between both motors......the 6 and 8 litre. I am just guessing on the chart however It appears that the 8 litre has close to 500 foot lbs of torque. That is huge in comparison to the 6 litre which shows about 320 foot pounds. Am I translating this correct do you think? Not only is the 8 litre strong in HP but it must be a huge torque monster and it is torque that counts as lets face it...we all run our boats in around that 3500 to 4500 rpm range.

magnum
10-31-2007, 05:20 PM
I have driven all MC boats with all three engines and the last was an x-star with the 8.1 we are looking at maybe to buy but it must have had the wrong prop on it , seemed kind of sluggish out of the hole, what is the stock prop size for 04 X-Star

MYMC
10-31-2007, 05:35 PM
I have driven all MC boats with all three engines and the last was an x-star with the 8.1 we are looking at maybe to buy but it must have had the wrong prop on it , seemed kind of sluggish out of the hole, what is the stock prop size for 04 X-Star
14.5x22...try a 13.7x19.5

magnum
10-31-2007, 06:41 PM
Does this one increase the whole shot torque? I failed to see what the RPM was at WOT but top speed was about 41, Is this 13.7x19.5 an over all performance prop? it has the stainless prop on it now but I think maybe if I do make a deal on it , it needs to go back to bronze

MYMC
11-01-2007, 10:41 AM
Does this one increase the whole shot torque? I failed to see what the RPM was at WOT but top speed was about 41, Is this 13.7x19.5 an over all performance prop? it has the stainless prop on it now but I think maybe if I do make a deal on it , it needs to go back to bronze
The overall performance will increase. Boat will have more hole shot and higher top speed. Material has nothing (well little) to do with it, but the stainless props were not as accurate as the CNC stuff. If you can make a deal on the boat you'll be impressed with the right prop on it.

skytop
11-03-2007, 12:13 AM
It's all to easy to simply say the obvious that "there is no substitute for cubic inches."
These days, I would also ad, "there is no substitute for a thick wallet to feed the thirst of an 8 litre engine". If gas were still .30 a gallon, we wouldn't be having this talk. But at a staggering $3.50 a gallon, reality bites hard.

The 8.1 liter engine will typically consume at medium cruise about 12-14 gallons per hour. Put the pedal to the metal, and burn it all up in no time flat with far higher consumption numbers. With gas about $3.50 a gallon (crude is now $96./ bbl) and continuing to rise, you must make each gallon work hard. Each average sized tank now cost about $300. to fill. That is serious money, my friends. If you have extra deep pockets and like burning money, than by all means go for the gusto. But remember that the new high performance 400 HP 6.2 litre engine will provide far better economy, less weight and offer over 90% of the performance of the big block.

No matter how it is calculated, it takes a lot more expensive fuel to fill the extra two litres of the big block. That's a whopping 1/3 more volume for only about 12-15% more power. Forget about the myth of running a big block at low rpm to yield better economy than a smaller engine. If that were true, Toyotas and Hondas would all have 427 cu in or hemi engines. The sheer weight and internal frictional losses of a large engine are far greater than a smaller more efficient engine.

For that relatively small improvement in acceleration and top end, you will indeed pay dearly. Ask yourself how many times you really require or need that maximum power. Remember with a Mastercraft hull, you do not have a racing design but rather a wakeboat designed to create wake by pushing water aside. Speed is always going to be moderate at best. You will never keep up with a Donzi or Fountain genre craft. Those are highly focused limited purpose speedboats. We all bought a Mastercraft for its versatility, comfort and quality.

Continually paying blood money for fuel gets old real fast. It inhibits your enjoyment and use of your boat.

06' X-2 R8R H8R
11-03-2007, 01:52 AM
Sometimes money isnt the option for pure adreline. BIGGER is always better, expecisally for resale

Holman J.B.F
11-03-2007, 03:56 AM
stop nagging ...europeans pay $ 7.67 a gallon. so those 3 bucks is a gift!...

uh..btw..i,m running propane ;)

cbryan70
11-03-2007, 12:50 PM
What does the propane conversion entail? IS propane alot cheaper over there? Why do most people over seas run propain? Same efficency?

Holman J.B.F
11-03-2007, 02:43 PM
lpg is 65% cheaper than gasoline,..the engine burns a little more on propane and there is a some performance loss on older impco kits.
The modern sequential gas injection lpg conversions are way better and have just a litlle or no power loss at all.
maybe it is just a matter of time before the first lpg converions on boats will take place in the u.s.a ...p.s a converion is only usefull if you make more than 150 hours a season...thet charge €2500,= for the conversion allone then you,ll need some tanks a 300 a piece i have 8
(second hand ones,..indoor forklift trucks use them alot)

anyway we burn about 140 liters(37 gallon) wakeboarding with the crew
at say 7.50 a gallon = 277.5 dollar a day on gasoline
on lpg it cost only 98 dollar

Holman J.B.F
11-03-2007, 02:44 PM
sorry posted it twice

MYMC
11-05-2007, 11:11 AM
It's all to easy to simply say the obvious that "there is no substitute for cubic inches."
These days, I would also ad, "there is no substitute for a thick wallet to feed the thirst of an 8 litre engine". If gas were still .30 a gallon, we wouldn't be having this talk. But at a staggering $3.50 a gallon, reality bites hard.

The 8.1 liter engine will typically consume at medium cruise about 12-14 gallons per hour. Put the pedal to the metal, and burn it all up in no time flat with far higher consumption numbers. With gas about $3.50 a gallon (crude is now $96./ bbl) and continuing to rise, you must make each gallon work hard. Each average sized tank now cost about $300. to fill. That is serious money, my friends. If you have extra deep pockets and like burning money, than by all means go for the gusto. But remember that the new high performance 400 HP 6.2 litre engine will provide far better economy, less weight and offer over 90% of the performance of the big block.

No matter how it is calculated, it takes a lot more expensive fuel to fill the extra two litres of the big block. That's a whopping 1/3 more volume for only about 12-15% more power. Forget about the myth of running a big block at low rpm to yield better economy than a smaller engine. If that were true, Toyotas and Hondas would all have 427 cu in or hemi engines. The sheer weight and internal frictional losses of a large engine are far greater than a smaller more efficient engine.

For that relatively small improvement in acceleration and top end, you will indeed pay dearly. Ask yourself how many times you really require or need that maximum power. Remember with a Mastercraft hull, you do not have a racing design but rather a wakeboat designed to create wake by pushing water aside. Speed is always going to be moderate at best. You will never keep up with a Donzi or Fountain genre craft. Those are highly focused limited purpose speedboats. We all bought a Mastercraft for its versatility, comfort and quality.

Continually paying blood money for fuel gets old real fast. It inhibits your enjoyment and use of your boat.
Um, interesting...is this based on experience or theory...because my experience over the last 10 years in the boat business and 20 years being an engine builder tells me very different, but hey never let the truth get in the way of a good post, this is the internet after all.

Blood money…good grief...how do you earn a living?

prostar205
11-05-2007, 12:02 PM
The 8.1 liter engine will typically consume at medium cruise about 12-14 gallons per hour. Put the pedal to the metal, and burn it all up in no time flat with far higher consumption numbers.


I assume you are basing your fuel consumption numbers on real world experience. As the owner of a boat (X-30) with the L-18 engine for the past 3 years, I can tell you your numbers are WAY OFF. I burn thru about 7-8 GPH no matter how loaded the boat is. I liken it to a diesel truck - it gets the same mileage (fuel consumption) no matter if it is loaded down or not. I could not be happier with the choice of engines in my boat and if I had to do it all over again, I would get the same engine in my next boat.

magnum
11-05-2007, 12:44 PM
MyMC, Do you have some data to post about the 8.1 as far a comparison on gas consumption or other detail that you have gathered over the years, I am interested , hopefully getting close to making a deal on an X-star with an 8.1

PendO
11-05-2007, 12:48 PM
Ask yourself how many times you really require or need that maximum power.

daily ...............................

We all bought a Mastercraft for its versatility, comfort and quality.

Continually paying blood money for fuel gets old real fast. It inhibits your enjoyment and use of your boat.

Why settle for versatility (it is overrated)

MYMC
11-05-2007, 03:47 PM
MyMC, Do you have some data to post about the 8.1 as far a comparison on gas consumption or other detail that you have gathered over the years, I am interested , hopefully getting close to making a deal on an X-star with an 8.1
Here is what I can tell you…
You only need look at Brake Specific Fuel Consumption (or BSFC). This is defined as the ratio between the engine's fuel mass consumption and the power it is producing. The fuel flow for BSFC calculations is expressed in pounds per hour (lb/hr) while the output is in horsepower (Hp) so, the formula for BSFC becomes: lb/Hp-hr . For an engine producing 200 horsepower, while using 100 pounds of gas per hour, the equation would be 100/200 = 0.50 BSFC. The great thing about BSFC #'s are that they remain similar over a wide range of engine sizes (if both are of same design and compression). For example, a one cylinder 50cc four-stroke and a 454ci V8 might both have a BSFC ratio of 0.45 lb/Hp-hr (when optimally tuned) at their respective peak torque points. So, if either of these engine's were overly rich, its BSFC might climb into the 0.55 to 0.65 range because the fuel flow in our equation will be going up as the power is going down. BSFC values all follow a hooked curve. At idle they run much higher - due primarily to the closed throttle pumping losses and excessive camshaft overlap. Minimum BSFC #'s occur at about the peak torque operating rage - the most fuel efficient (per Hp) operating point for an engine. As RPM increases towards peak power, the BSFC rises again, since more fuel energy is consumed just overcoming the speed induced friction and breathing restrictions. So then where does this leave us?

MCX 350hp will use about 26 gallons per hour at WOT
LY6 400hp will use about 30 gallons per hour at WOT (+14% more fuel, 12.5% more HP and 15% more torque over MCX)
L18 450hp will use about 34 gallons per hour at WOT (+24% more fuel, 23% more HP and 32% more torque over MCX)

Now we need to consider what makes the boat move…torque (defined as the ability to do work)…and taking what you learned above (the fuel consumption differences are less at the torque peak) then add the benefit of the greater ability to do work (more torque output) of the larger engines you can clearly see where this is all headed. THERE IS NO SUBSTITUE FOR CUBIC INCHES! Sure efficiency plays a role…but translate those efficiency gains to the larger engine and it will always make more power. Yes, there are greater pumping & frictional losses due to size; however, they are not relevant when it comes to a boat. Why? Hull drag. Viewed another way…if you run your boat at WOT every time you use it, the L18 will cost you $32 per hour more. Of course it will retain +$14,000 in additional value over the MCX at the end of year one (look at the current NADA book), so you should be good for 437.5 hours of WOT operation before it gets even!

(To everyone reading this there are some assumptions that must be made to arrive at the numbers, but the outcome won’t change. I am using .46 BSFC and unleaded fuel at 72 degrees weighing 6.25 lbs/gallon…I didn’t do this to be exact but to prove a point)

PendO
11-05-2007, 04:55 PM
If this thread were close and mike's comments posted at the top ... we could save a lot of bandwidth over the winter

MYMC
11-05-2007, 06:17 PM
If this thread were close and mike's comments posted at the top ... we could save a lot of bandwidth over the winter
Thank you sir...it does seem as if this question comes up quite often over the fall/winter.

skytop
11-05-2007, 09:07 PM
Say gang....
Not looking to start with anyone.

I am offering a clarification of the difference in operating expense between the 6L and 8.1 L engines. Not talking about the undeniable fun factor but rather the cost and waste factor.

I won't offer my opinion to keep facts objective but rather refer to a recent sea trial that documents the remarkable thirst of the big block at various speeds.

The subject boat is a very recent X-45 equipped with a 450 hp L-18 engine equipped with a 14"x22" four blade prop. The boat is carrying 3 people aboard. As speed rises to 44 mph, the engine consumed a whopping 31 to 33 gallons per hour. Even at a more modest 40 mph, the engine consumes 23 gallons per hour. 31 gallons/hr is well over $100.+ an hour and dramatically limits cruising time due to tank capacity.
Article reference:
http://www.motorboating.com/motorboat/seatrials/article/0,12696,1051533,00.html

Pushing a Mastercraft hull at any speed above 40 mph requires serious power. Remember you are now pushing an ever increasing wall of very heavy water aside, even on plane. Approaching a 'scalding' 50 mph or greater speed requires an ever increasing level of big block power which translates into yet larger fuel consumption.

Today's Associated Press Business News states that as the new high crude prices of today trickle down to the currently insulated consumer level, this summer will bring $4.+ a gallon regular gasoline. As we know, marinas will probably be charging closer to $5. Choose your poison.

How about resale? The L-18 engine will set you back about $10,000. and then you must pay to feed it, big time. Will you get any of that back? Maybe. But consider this historical FACT. In the immediate post gas crunch years of 1974-1980, muscle cars like 427 Vettes, Hemi Cudas, 454 Chevelles, 455 Goats and GSX's, 440 Chargers, etc. dropped in value. The floor fell out of the musclecar market. In spite of super desireablility, no one would buy. Irrefutable market dynamics dictate that prices will drop. It's undeniable and simple. The market abhors hogs and waste in a violently escalating fuel cycle.

Not opinion, just fact.

cbryan70
11-05-2007, 09:41 PM
This is true but i would say MOST people that are purchasing a new boat that is close to the 100,000 doller range gas prices usually are not that big of an issue. People who work with large doller boats during the large recessions actually did not see a large decrease in boat sales. Large boats being 30 plus. but with that being said mastercraft boats are priced, lets face it to the upper class of america. Most of these people can still afford the boats during bad economy so one would think they woudl also beable to afford the gas to feed them. i do see your point tho as next summer if gas reaches 4 dollers a gallon it will effect me and my boating habits. it will have to consist of less messing around ideling or cruising and more drinking inbetween sets! ;-)

east tx skier
11-05-2007, 11:46 PM
I wasn't aware that any of these boats, other than the old barefoot outboards, would do over 36 mph. ;)

sand2snow22
11-06-2007, 12:00 AM
MCX 350hp will use about 26 gallons per hour at WOT


I'd be out of gas in 1 hour and 17 minutes!

X-Aggie
11-06-2007, 01:43 AM
L18 450hp will use about 34 gallons per hour at WOT

So that means I will enjoy 12 1/2 min of fun before I run out of gas...


I can only afford to put a $20 spot in per weekend.:cry:

PendO
11-06-2007, 02:00 AM
Interesting read, but if we are to make a real comparsion we need the same chart for all of the engines ... and I'd be more interested in the numbers for typical boarding, surfing, and crusing speeds ... and lets do it with 2500# of ballast and 8 people ...

1boarder
11-06-2007, 09:34 AM
Not wanting to add fuel to the fire, but according to the owners manual both motors can only pump 1 pint of fuel every twenty seconds or 22.5 gallons an hour max.

MYMC
11-06-2007, 10:21 AM
How about resale? The L-18 engine will set you back about $10,000. and then you must pay to feed it, big time. Will you get any of that back? Maybe. But consider this historical FACT. In the immediate post gas crunch years of 1974-1980, muscle cars like 427 Vettes, Hemi Cudas, 454 Chevelles, 455 Goats and GSX's, 440 Chargers, etc. dropped in value. The floor fell out of the musclecar market. In spite of super desireablility, no one would buy. Irrefutable market dynamics dictate that prices will drop. It's undeniable and simple. The market abhors hogs and waste in a violently escalating fuel cycle.

Not opinion, just fact.
And from the where are they now file:
http://cgi.ebay.com/ebaymotors/Plymouth-Barracuda-1970-Plymouth-Cuda-AAR-4-SPEED-NUMBERS-MATCHING_W0QQitemZ250181623695QQihZ015QQcategoryZ6 409QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
or
http://cgi.ebay.com/ebaymotors/Chevrolet-Corvette-427-390-HP-1967-CORVETTE-ROADSTER_W0QQcmdZViewItemQQcategoryZ6168QQihZ012QQ itemZ220167094908QQrdZ1QQsspagenameZWDVW

Don't be a hater!